In winning control of the House of Representatives, Democrats take over the chairman’s seat in the chamber’s committees. Here are the men and women likely to be setting the agenda for key committees, and what policy changes to expect from them.

House Ways & Means Committee

Rep. Richard Neal PHOTO: TOYA SARNO JORDAN/GETTY IMAGES

Massachusetts Rep. Richard Neal is poised to get the post he’s been eyeing for years: The chairmanship of the House Ways and Means Committee, which has jurisdiction over taxes, trade, health care and Social Security. Mr. Neal, the 69-year-old former mayor of Springfield, Mass., was first elected to Congress in 1988 and represents the western part of the state.

Mr. Neal took over the panel’s top Democratic spot from retiring Rep. Sander Levin of Michigan and is unlikely to face a challenge within the party.

As chairman, Mr. Neal would try to strengthen the Affordable Care Act, roll back some of last year’s tax cuts and promote policies to encourage more saving in retirement accounts. He would also gain the power to obtain and analyze President Trump’s tax returns, giving Ways and Means an important piece of the oversight authority Democrats can exercise.

Mr. Neal would succeed Rep. Kevin Brady of Texas, the chief author of the 2017 tax law. No Democrats voted for the law, and the Ways and Means panel is where the party will begin holding hearings on the law’s effects and sorting out its alternative proposals as Democrats aim for control of the White House in 2021.

— Richard Rubin

House Committee on Energy and Commerce

Rep. Frank Pallone Photo: Joe Raedle/Getty Images

The Energy and Commerce Committee oversees health-care legislation in the House. Rep. Frank Pallone has been the top Democrat on the committee since 2014 and is expected to ascend to the chairman position.

Mr. Pallone, 66 years old, has served in Congress since 1988, representing coastal New Jersey. In his time in Congress, he has largely focused on health-care policy and environmental issues, specifically to stop ocean dumping and offshore oil and gas drilling in the Atlantic region.

He plans to meet with members to discuss plans to lower health-care and prescription drug costs for consumers, a core plank of House Democratic lawmakers’ agenda for the next Congress. Mr. Pallone would also like to increase support for Medicaid in order to combat the opioid epidemic, as many people who need treatment use government health care.

Mr. Pallone also promised members that they would conduct stronger oversight of the Federal Communications Commission, which the committee oversees. The lawmaker said that Congressional supervision of the agency had been lacking during the Trump administration.

—Natalie Andrews

House Financial Services Committee

Rep. Maxine Waters Photo: andrew caballero-reynolds/Agence France-Presse/Getty Images

California Rep. Maxine Waters is the front-runner to become the new chairwoman of the House Financial Services Committee, and would be both the first woman and African-American to head the panel.

Ms. Waters is the ranking Democrat on the committee, and is widely expected to chair it. Next in line would be Rep. Carolyn Maloney of New York.

Ms. Waters has spent more than three decades as a politician representing the Los Angeles area, in the California assembly and, since 1990, the U.S. House. She has been one of the most aggressive Democratic critics of President Trump.

She has said she would make housing finance a top priority. The committee also faces thorny debates around marijuana banking, financial technology, and government insurance for floods and terrorist attacks. Ms. Waters also is likely to probe big banks and the Trump administration, including the Treasury Department and other agencies her committee oversees. She has previously suggested that Wells Fargo & Co. should be broken up for repeated consumer abuses, and demanded information on Deustche Bank AG’s loans to Mr. Trump. But she hasn’t wielded the subpoena authority that comes with the chairman’s gavel. On the regulatory front, a likely target is the Consumer Financial Protection Bureau. Democrats helped created the new agency in 2010 and believe GOP leadership is trying to neuter it.

Her elevation will present a striking contrast to the Republicans on the committee, who have praised Trump-nominated financial regulators, pursued legislation to roll back bank rules, and generally avoided publicly grilling Wall Street executives. Ms. Waters is expected to change tack on all counts. She also could shift gears on oversight of the Federal Reserve. She is less likely than Republicans to seek limits on the Fed’s discretion in steering the economy, and more likely to focus on other issues such as the Fed’s big-bank rules, and how Fed policies impact minorities and the poor.

—Ryan Tracy

House Permanent Select Committee on Intelligence

Rep. Adam Schiff Photo: Alex Brandon/Associated Press

Rep. Adam Schiff of California is the current ranking member and has earned wide praise from fellow Democrats for his handling of the politically sensitive investigation into Russian interference in the 2016 election. A former federal prosecutor, Mr. Schiff is 58 years old and has served in Congress since 2001.

The future leadership of this panel is dependent on the outcome of the speaker’s race. Unlike other panels, the membership of the intelligence committee is entirely at the direction of congressional leadership.

The custom is that a Democrat can serve four years as ranking member or chairman. Mr. Schiff has already spent four years as ranking member. He is a close ally of House Minority Leader Nancy Pelosi, who is widely expected to keep him on despite the custom. However, Ms. Pelosi may not have the support within the Democratic caucus to win the speakership. If Mr. Schiff doesn’t become chairman, Rep. Jim Himes of Connecticut has the most seniority and is a respected member of the panel.

If Democrats retake the House, they’re likely to reopen the investigation into Russian election interference during the 2016 campaign. The panel’s Democrats dissented from the report issued by the GOP majority, saying that major lines of inquiry went unexplored.

Rep. Devin Nunes (R., Calif.) is the outgoing chairman of the panel. Under his tenure, relations on the committee sunk to new lows—mostly over his handling of the panel’s Russia investigation. Notably, he pursued a politically divisive investigation into the origin of a surveillance warrant on a Trump adviser during the presidential campaign and was forced to step aside from leadership of the panel’s Russia investigation over his closeness with the White House.

—Byron Tau

House Appropriations Committee

Rep. Nita Lowey Photo: Zuma Press

Rep. Nita Lowey of New York, the panel’s top Democrat, is expected to become its next chairwoman, making her the first woman to lead the powerful panel. Ms. Lowey, 81 years old, is now in her 15th term in the House and a longtime fixture on the Appropriations Committee.

A reliable ally of House Democratic leaders, Ms. Lowey would take the lead writing the spending bills needed to fund the government. Congressional leaders typically strike an agreement on the overall funding level, but leave it to the appropriations panel to divvy it up between agencies.

She is expected to write dramatically different bills from those drafted by its current chairman, Rep. Rodney Frelinghuysen (R., N.J.), who is retiring in the face of a tight re-election campaign. Ms. Lowey has championed women’s reproductive rights and teen-pregnancy prevention, and wouldn’t seek to block Planned Parenthood from receiving federal funding, as House Republicans have sought.

She has also advocated for gun control and would seek new funding for the Centers for Disease Control and Prevention to research gun violence. Under Ms. Lowey, Democrats on the committee would also be expected to push to head off oil drilling in the Arctic National Wildlife Refuge and fund more research into climate change. Under Mr. Frelinghuysen, the House’s spending bills included many of President Trump’s priorities, including $5 billion in funding for the border wall, which Democrats oppose.

—Kristina Peterson

House Foreign Affairs Committee

Rep. Eliot Engel Photo: zach gibson/Agence France-Presse/Getty Images

Rep. Eliot Engel of New York is in line to take over the House Foreign Affairs Committee. Mr. Engel, 71 years old, is a veteran of Congress since 1989, representing parts of the Bronx and Westchester County.

He isn’t expected to be challenged for the job. But other members of the panel to watch as potential leaders if Mr. Engel falls short: Reps. Gerry Connolly of Virginia, Gregory Meeks of New York or David Cicilline of Rhode Island.

The House Foreign Affairs Committee is typically less partisan than most panels given its focus on such foreign policy issues as human rights, democracy promotion and the impact of U.S. decisions around the globe. But under Democratic leadership, there will be questions about the Trump administration’s management of the State Department, diplomatic decisions around Iran, North Korea and Israel as well as other topics.

The outgoing chairman, Rep. Ed Royce of California, is retiring from Congress after reaching a term limit for his leadership of the panel. From the perch, he had been a harsh critic of the Obama administration. In the Trump years, he has focused on issues like human trafficking and terrorist financing.

—Byron Tau

House Armed Services Committee

Rep. Adam Smith Photo: Chip Somodevilla/Getty Images

Washington Rep. Adam Smith, the ranking Democratic member of the House Armed Services Committee, is expected to get the nod to become chairman. Mr. Smith, 53, would succeed Texas Republican Rep. Mac Thornberry, who has chaired the committee for the last three years. Mr. Smith, a one-time Washington state senator, was elected to the House of Representatives in 1997. He has been Armed Services ranking member since 2015.

The Armed Services Committee, dealing with military matters, has a tradition of bipartisanship, and Mr. Smith has worked with Mr. Thornberry on legislation including military policy and spending bills.

Mr. Smith has also been a champion of Democratic positions. Earlier this year, he opposed a Trump administration proposal—which ultimately was dropped—to use Pentagon funds to start construction of a southern U.S. border wall.

The next few years are seen as critical for the committee. The Pentagon’s budget, now free of budget caps, is expected to level off after next year, posing a challenge to efforts to fund military readiness improvements—training, equipment and force strength—as well as modernization and procurement efforts needed to counter a rising China and a more aggressive Russia.

During his tenure, Mr. Thornberry has focused on military preparedness, improving acquisition, and bolstering the defense budget. He has also pushed for reforms within the Pentagon to save money on overhead.

—Gordon Lubold

House Judiciary Committee

Rep. Jerrold Nadler Photo: Michael Brochstein/Zuma Press

Rep. Jerrold Nadler is the favorite to become the new chairman of the Judiciary Committee. A New York City Democrat, Mr. Nadler, 71 years old, represents a district that encompasses the west side of Manhattan, lower Manhattan and several neighborhoods in Brooklyn. He’s a veteran of the 1998 impeachment of Bill Clinton, having served on the Judiciary Committee and become something of an expert on impeachment proceedings.

Mr. Nadler was elected to the top Democratic spot on the committee by his peers after the resignation of Michigan Rep. John Conyers earlier this year and is expected to easily become chairman. If he falls short, California Rep. Zoe Lofgren has also expressed interest in the job.

Democrats on the panel have vowed to conduct aggressive oversight of Mr. Trump’s relationship with the Justice Department, the FBI and the special counsel’s office. The panel is also the front line of defense on questions of impeachment and executive wrongdoing. Beyond that, Mr. Nadler has said he would like to take up legislation to curb gun violence.

The current Chairman Rep. Bob Goodlatte (R., Va.) is retiring from Congress. Under his leadership, the panel has been conducting a politically charged investigation into whether there was any bias at the Department of Justice or FBI during the 2016 campaign.

—Byron Tau

House Committee on Oversight and Government Reform

Rep. Elijah Cummings Photo: Tom Williams/Zuma Press

Maryland’s Rep. Elijah Cummings is expected to take over the reins of Congress’s most powerful investigative body. Elected in 1996, Mr. Cummings represents a district that encompasses a large part of Baltimore. He’s a veteran of congressional oversight fights—he’s been the top Democrat on the panel since 2010 and also served as the ranking member of the contentious House Benghazi committee which investigated the 2012 terrorist attack.

Mr. Cummings isn’t expected to face any internal challenges for the job this year. But Rep. Gerry Connolly of Virginia is considered a top contender for the chairmanship at some point. He represents a suburban Washington district and has extensive experience dealing with federal workforce and oversight issues. Rep. Carolyn Maloney of New York has the most seniority on the panel and also has previously run for the top job.

Democrats on the committee expect to pursue a robust investigative agenda that will touch on many of the controversies in the Trump administration. The panel has a wide mandate to look for waste, fraud and abuse anywhere in the federal government. Democrats are expected to look into Mr. Trump’s possible business conflicts of interest, personnel decisions within the administration, spending decisions, guilty pleas by Trump confidants and many other issues that should make the oversight panel one of the busiest.

The current chairman is Republican Rep. Trey Gowdy of South Carolina, who is retiring from Congress. He believed in a very narrow mandate for the job, keeping the panel focused on such issues as the census, postal reform and streamlining government programs. Mr. Gowdy’s approach drew criticism from Democrats, who said Congress has abdicated its responsibility to conduct aggressive oversight of Mr. Trump and his subordinates.

—Byron Tau

House Transportation and Infrastructure Committee

Rep. Peter DeFazio Photo: Chip Somodevilla/Getty Images

Rep. Peter DeFazio of Oregon, the committee’s ranking Democrat, would be the favorite to become chairman. Mr. DeFazio, 71 years old, is now serving his 16th term in Congress, representing coastal counties south of Portland to the California border. A former congressional aide, he served as a county commissioner before being elected to Congress in 1986.

From his position in the Democratic minority, Mr. DeFazio has expressed a willingness to work with the Trump administration. He was among the Democrats who initially applauded Mr. Trump’s talk of a major federal infrastructure-rebuilding effort, only to denounce the administration’s eventual proposal, which would have relied on local governments to raise the majority of the money. Mr. DeFazio labed that idea a “scam.”

Mr. DeFazio would succeed Rep. Bill Shuster of Pennsylvania, who is retiring from Congress. Mr. Shuster was able to win committee support, and backing from Mr. Trump, for a plan to privatize the country’s air traffic control system, but was thwarted by opposition in the Senate. A five-year reauthorization of the FAA that passed both chambers left out Mr. Shuster’s privatization proposal. Mr. DeFazio likewise opposes the privatization plan.

Mr. DeFazio would also likely take a tougher line on commuter and freight railroads that have failed to meet deadlines to install anti-crash technology called “positive train control” or PTC. PTC was first mandated in 2008, and Mr. DeFazio has voiced frustration at the slow pace of installation, even after Congress extended it to the end of 2018.

—Ted Mann

House Committee on Agriculture

Rep. Collin Peterson Photo: Tom Williams/Zuma Press

Rep. Collin Peterson, a Minnesota Democrat who served as the Agriculture Committee’s chairman from 2007 through 2010, is expected to regain the panel’s helm.

Mr. Peterson, 74 years old, worked as a certified public accountant before he was elected to the House in 1990. One of the House’s most conservative Democrats, Mr. Peterson represents a rural, agricultural district that President Trump won by more than 30 percentage points in 2016. His district is so large that he often travels around it in a single-engine plane.

Mr. Peterson is known for taking a bipartisan approach to farm legislation—as well as to some of his hobbies. He has played guitar in several rock bands with lawmakers from both parties, including one called “The Second Amendments.”

The House earlier this year passed a farm bill drafted by Chairman Mike Conaway (R., Texas) that tightened work requirements for those receiving food stamps. Mr. Peterson opposed that provision and would likely make more modest tweaks to the food-stamp program in upcoming farm legislation. He is also expected to pay special attention to the commodities biggest in his district, including sugar beets and dairy, as well as animal health.

—Kristina Peterson

House Committee on Homeland Security

Rep. Bennie Thompson Photo: Bill Clark/Zuma Press

The clear frontrunner for the chairmanship is current ranking member Rep. Bennie Thompson, 70 years old. He is a senior Democrat from Mississippi who has been a member of the committee since its origins 16 years ago, when the U.S. was entering the post-9/11 era. When the Democrats took control of the House in 2006, Mr. Thompson served as its chairman and it’s widely expected that he would resume the role.

Though the Homeland Security Committee has historically worked in a bipartisan fashion, there has been some tension in recent months between Mr. Thompson and the current chairman, Texas Republican Rep. Michael McCaul, who could become the ranking member in the next Congress should the GOP lose its majority.

Mr. Thompson has criticized Mr. McCaul for not spending enough time focusing the committee on the issue of election security and the integrity of U.S. elections, a topic Mr. Thompson is expected to focus on when he resumes the chairmanship.

—Joshua Jamerson

House Committee on Natural Resources

Rep. Raúl Grijalva Photo: Susan Walsh/Associated Press

Arizona Rep. Raúl Grijalva, currently the ranking Democrat on the Natural Resources Committee, is poised to become the chairman. A co-chair of the Congressional Progressive Caucus, Mr. Grijalva is a liberal member of the party and has served in Congress for more than a decade.

“I see nobody else on the committee challenging him for the expected chairmanship,” said Nick Rahall, a former Congressman who led the Natural Resources committee the last time Democrats controlled the House.

The committee is likely to dig into the performance of Interior Secretary Ryan Zinke, according to a Democratic aide, investigating his alleged involvement in a Montana real-estate deal backed by oil magnate Halliburton , which he has denied. Mr. Grijalva will also take steps to enhance environmental protections and restrictions on the use of federal land, while current Republican committee Chairman Rob Bishop has sought to roll them back.

—Andrew Duehren

House Committee on Education and the Workforce

Rep. Bobby Scott Photo: Toya Sarno Jordan/Getty Images

Virginia Rep. Bobby Scott, the first African-American to serve in the House’s Virginia delegation since reconstruction, will take the helm of the Education and the Workforce Committee.

A lifelong advocate for increased student and worker protections, Mr. Scott is likely to take up a reauthorization of the law governing higher education next year. A draft bill released by committee Democrats in July shows they would likely concentrate on college affordability, in part by making federal financial aid more generous and cracking down on for-profit colleges using unethical recruiting practices that leave students with long-term debt they can’t pay back. One area the bill is unlikely to touch: free college, an idea popular with the left that many democratic policymakers think unworkable.

Mr. Scott, who opposed the nomination of Education Secretary Betsy DeVos, is also likely to call her in for more committee hearings, on issues ranging from guns in schools to civil rights protections and the secretary’s agenda to deregulate the for-profit college industry.

Mr. Scott, 71 years old, has also expressed interest in several hot-button labor issues, including raising the minimum wage to $15 an hour and pushing mandatory paid family leave. His committee has introduced additional legislation that would increase labor-union protections, after a Supreme Court decision in June gutted a core pillar of public-sector union strength.

Also, look for the newly-Democratic committee to weigh a name change—to the Committee on Education and Labor—its erstwhile title until Republicans under former Republican House Speaker Newt Gingrich adopted the word “workforce,” a word preferred by employers. The committee’s name has seesawed along with control of Congress ever since.

—Michelle Hackman

House Committee on Rules

Rep. Jim McGovern Photo: Alejandro Ernesto/Zuma Press

Massachusetts Rep. Jim McGovern is expected to chair the Rules Committee, which decides how or if legislation can be debated or changed when it comes to the House floor.

One of the first agenda items in the new Congress is to pass a rules package dictating how it will be run. Under the direction of Minority Leader Nancy Pelosi, Mr. McGovern, 58 years old, has been meeting with Democrats and Republicans to see what rules changes lawmakers want to see.

Mr. McGovern assumed the post of top Democrat on the committee when Rep. Louise Slaughter, the ranking Democrat, died in March. Because the Rules Committee follows seniority rules, he is seen as the most likely chairman.

Mr. McGovern may focus on allowing more members to offer amendments to legislation on the floor and have wider debates on legislation. The Republican chairman, Rep. Pete Sessions, approved a record-setting number of closed rules to the House floor—meaning that no amendments were allowed.

The rules package may also focus on ethics reforms, such as banning members of the House from serving on the boards of publicly held companies.

The voting rights of House delegates, which represent U.S. territories and Washington D.C., could also change. When Democrats held the House from 2008 to 2011, they expanded the voting rights of delegates—though only so that the vote had no ultimate effect on a measure’s outcome. When Republicans took the majority, they removed those privileges. Of the six nonvoting delegates, the majority are Democrats, so the Rules Committee could change the rules to expand their voting power.

Mr. McGovern has a long history with the committee. From 1982 to 1996, Mr. McGovern worked as an aide for the then-chairman of the Rules Committee. He was elected to Congress in 1996.

—Natalie Andrews

House Committee on Veterans Affairs

Rep. Mark Takano Photo: Bill Clark/Zuma Press

The top-ranking Democrat on the House Veterans Affairs Committee, Rep. Tim Walz of Minnesota, announced last year that he wouldn’t run for re-election to his House seat this year to vie for the governorship of his home state, leaving unclear who would lead the committee in the event of a Democratic takeover in the House.

Mr. Walz assumed the ranking-member role after a brief fight for the job with fellow Democrat Rep. Mark Takano of California, who eventually conceded the position and was named vice ranking member.

Mr. Walz hasn’t said who he is supporting to become the top Democrat on the committee. Mr. Takano, 57 years old, has been filling in as de facto ranking member when Mr. Walz is on the gubernatorial campaign trail and unable to attend hearings, and he appears to be the frontrunner.

However, he will face a battle with fellow California Rep. Julia Brownley, 66 years old, to take the gavel, according to people familiar with the matter. Ms. Brownley said months ago she would seek the top spot.

Rep. Julia Brownley Photo: Bill Clark/Zuma Press

Both Democrats arrived in Congress in 2012 and have become well known for their work on veterans issues, with Ms. Brownley serving as the top Democrat on the subcommittee that deals with veterans’ health care. Mr. Takano regularly grills Department of Veterans Affairs officials at hearings and has demonstrated a willingness to spar with the Trump administration on key issues.

In the next Congress, lawmakers likely will focus on the process of instituting a new law regarding private care for veterans and a handful of other measures passed in the first two years of the Trump administration. The committee likely won’t focus on crafting extensive new legislation. Instead, it will work out its oversight role for the VA, which has undergone regular leadership and policy changes since a 2014 wait-time scandal brought attention to the department and its shortcomings.

—Ben Kesling