The cast of characters waiting in the wings to chair powerful Senate committees if Republicans win the majority this November would radically shift the direction of the chamber and probably make life miserable for the White House.

It wouldn’t be the majority leader’s choice. GOP committee members would vote on them, although sources say senators tend to negotiate and agree upon the assignments ahead of time. Based on seniority, conversations with Republican sources and the quirks of internal conference rules with regard to committees, here’s who is best positioned to chair the various panels under a GOP majority.

Judiciary Committee

In line to helm this committee would be Sen. Chuck Grassley (R-IA), the panel’s ranking member since 2011. As chairman of one of the most powerful committees in the Senate, he’d be tasked with oversight of the Obama administration — including its actions on crime, terrorism, immigration, and administrative actions — and putting judges on the courts. He’d be the counterpart to House Oversight Chair Darrell Issa (R-CA) in searching for White House scandals and seeking to embarrass the president.

Finance Committee

The next chairman would probably be Sen. Orrin Hatch (R-UT), the ranking member since 2011. The influential panel — which has jurisdiction over taxes, entitlements and health spending — is a chief mover and shaker in the Obamacare debate. Hatch has been a thorn in the White House’s side, and as chairman his investigative powers would be greatly expanded.

Environment & Public Works Committee

Leading the committee would likely be Sen. James Inhofe (R-OK), who was chairman for four years before Republicans lost their majority in 2007. He’ll have two more years in the role under the Senate GOP’s self-imposed six-year term limit. Inhofe has taken a keen interest in the committee’s subject matter, becoming the Senate’s most outspoken denier of the scientific consensus that climate change is real and man-made.

Armed Services Committee

Sen. John McCain (R-AZ) would have seniority to chair the panel, which oversees the military and national security issues. McCain, a leading Republican voice on security and terrorism, is a frequently critic of his 2008 rival on national security matters, and his hypothetical perch at Armed Services would make him an obstacle for Obama.

Budget Committee

Sen. Jeff Sessions (R-AL) is currently the top Republican and presumably next in line to be chairman. He’s a fervent supporter of Rep. Paul Ryan’s (R-WI) efforts to remake the federal budget and a strong critic of welfare programs. But sources say Sen. Mike Enzi (R-WY), a senior budget member, may also run for the chairmanship.

Health, Education, Labor and Pensions Committee

This committee would likely be led by Sen. Lamar Alexander (R-TN), the current ranking member, and a close ally of McConnell. The panel has jurisdiction over a variety of domestic issues affecting middle income and poor people, including Obamacare to an extent.

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Next in line to chair other committees: Sen. Bob Corker (R-TN) at the Foreign Relations Committee, Sen. Richard Shelby (R-AL) at the Appropriations Committee, Sen. Mike Crapo (R-ID) at Banking Committee and Sen. Mike Enzi (R-WY) at the Homeland Security Committee (if he doesn’t lead the Budget Committee).