(Bloomberg) — The Senate Judiciary Committee will get a jolt when Republican Charles Grassley becomes chairman and pursues investigations that could tarnish President Barack Obama’s legacy.

Even while in the minority on the panel, he scrutinized the Justice Department’s botched effort to track guns illegally shipped to Mexico.

“It’ll be full employment for a lot of lawyers in town who advise clients on Capitol Hill, and the White House counsel would have to staff up again,” Jim Manley, a former aide to Senate Democratic leader Harry Reid, said in a phone interview. Grassley is “especially into investigations of waste, fraud and abuse,” Manley said.

All Senate committee will be getting new leaders when Republicans take control of the Senate in January.

As the Judiciary panel’s top Republican, Grassley used his staff to investigate the Justice Department’s Operation Fast and Furious, which allowed illegal gun purchases in the U.S. in an effort to link the weapons to Mexican cartels.

Panel chairmen “have a tremendous amount of power,” said Ron Bonjean, a Republican strategist and onetime aide to former Senate Majority Leader Trent Lott. “They are akin to Mafia bosses, basically.”

Republicans gained at least seven Senate seats in the Nov. 4 election and expanded their House majority. For now, Democrats keep their 55-45 Senate control in the lame-duck session that begins today. Among the priorities for the session are funding the government after Dec. 11, reviving lapsed tax breaks and financing the fights against Ebola and Islamic State.

Grassley is in line to replace Sen. Patrick Leahy, a Vermont Democrat, as Judiciary chairman.

“Oversight is too often overlooked as Congress focuses on new legislation,” Grassley said in an e-mailed statement this week. “My goal is to promote transparency and accountability and restore the committee’s role as a true check on the massive and powerful federal bureaucracy.”

He’ll probably wield the gavel as senators question Loretta Lynch, Obama’s nominee to become attorney general, during confirmation hearings. Mitch McConnell, a Kentucky Republican set to be Senate majority leader, wants to delay Lynch’s confirmation vote until 2015.

Budget 

 

On the Senate Budget committee, top Republican Jeff Sessions of Alabama will probably become chairman, taking over from Sen. Patty Murray, a Washington Democrat.

Sessions is “not one who has in the past been bipartisan in his negotiating,” said Michele Swers, an associate government professor at Georgetown University in Washington.

Sessions said in a statement the “immediate emergency” facing Republicans is Obama’s “disastrous planned actions” on immigration. The president said last week he’ll act by year’s end to halt deportations for some undocumented immigrants if Congress doesn’t move to rewrite the law.

Appropriations

Thad Cochran, the Mississippi Republican in line to be Appropriations Committee chairman, “will be less partisan than some of his colleagues in terms of running his committee,” said James Thurber, director of the Center for Congressional and Presidential Studies at American University in Washington.

This will be Cochran’s second time in the job after holding it from 2005 to 2007. He’ll take over from Maryland Democrat Barbara Mikulski.

“He’s a legislator who respects the institution; he’s not a bomb-thrower,” Thurber said in a phone interview. Cochran probably would ensure Democrats on the committee can secure some funding for their local projects, instead of ostracizing them, he said.

Finance and Banking

Republican chairmen of the Finance Committee and the Banking Committee, may get help from Democrats in pursuing some of their goals.

Orrin Hatch, the Utah Republican who is currently the top Republican on the Senate Finance Committee, is expected to take the gavel from current chairman Ron Wyden, an Oregon Democrat.

The Republican-led Senate should pursue tax-law changes and “strike away” at the Patient Protection and Affordable Care Act (PPACA) — Obama’s health-care law, Hatch said in an e-mailed statement.

Thurber said that may include an effort to repeal a tax on medical devices, such as pacemakers and defibrillators, that’s supposed to help pay for PPACA. That levy is also opposed by a number of Democrats. Boston Scientific Corp. is among the device makers that have fought to repeal it.

Richard Shelby, an Alabama Republican who was Banking Committee from 2003 to 2007, is expected to resume that post and replace retiring Democrat Tim Johnson of South Dakota.

Shelby is unlikely to seek action on more than 20 bills passed by the Republican-led House to unravel the 2010 Dodd-Frank financial law. Instead, he’s expected to seek bipartisan support to weaken parts of the law, which he opposed, current and former congressional aides have said.

Those may include eliminating the director’s job at the Consumer Financial Protection Bureau and requiring more disclosure by the Financial Stability Oversight Council.

The House

Senate Republicans generally award committee chairmanships to the senior party member on a panel. Still, seniority alone doesn’t guarantee the top position, especially in the House.

Most House panel leaders are expected to stay the same as Republicans remain in power. One exception is the Ways and Means Committee, where Paul Ryan, the Wisconsin Republican who now leads the Budget panel, and Rep. Kevin Brady of Texas have both said they want the gavel. 

–With assistance from Derek Wallbank, Richard Rubin, Kathleen Hunter, Cheyenne Hopkins, Mark Drajem and Caitlin Webber in Washington.

Copyright 2018 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.