Regardless of whether Republicans or Democrats win control of the Senate in November, the chamber will face significant changes in some of its most influential leadership and policy posts over the next two years.

A Democratic takeover would clearly produce the most far-reaching upheaval, extending from the post of majority leader through every committee and subcommittee chairmanship, and producing a dramatic shift in political priorities for the chamber.

But major changes will also occur if Republicans keep their current majority, starting in January with a wrenching game of musical chairs at several key committees, prompted by term limits that GOP senators imposed on themselves in the mid-1990s.

GOP chairmanship changes are in store for the Appropriations, Judiciary, Commerce, Budget and possibly Intelligence committees, with ripple effects for the panels dealing with agriculture and with health and education policy. Democrats have no term limits, so, with some exceptions, Democratic chairmen would pick up where they left off when they lost control of the Senate to Republicans in the 2002 elections.

For Republicans, there will be additional chairmanship changes in 2006 and, even more important, a wholesale reshuffling of GOP leadership posts, prompted by the anticipated retirement of Majority Leader Bill Frist (Tenn.) and a domino effect on other jobs. Throughout the period, maneuvering is anticipated by GOP senators -- including Sens. Rick Santorum (Pa.), John McCain (Ariz.), Chuck Hagel (Neb.), George Allen (Va.) and Frist -- all of whom appear to be interested in running for president in 2008.

"It'll be like a new season of 'The Sopranos,' with plots and subplots, betrayals and vendettas," said John J. Pitney, a political science professor at Claremont McKenna College in California and former GOP aide who keeps a close eye on the politics of Congress.

While there is certain to be a new face on the Senate leadership, the changes in the lineup will not necessarily reflect major shifts in policy, ideology or political strategy.

For instance, although Sen. Thad Cochran (R-Miss.), who will succeed Sen. Ted Stevens (R-Alaska) as Appropriations chairman, is arguably a bit more conservative than Stevens, it is money and geography rather than ideology that drives appropriators of both parties. In other words, Mississippi may be the big winner -- and Alaska the big loser -- in exchanging Cochran for Stevens.

"They'll be resetting their compasses from northwest to southeast," quipped Ross K. Baker, a political scientist and Congress-watcher at Rutgers University. Stevens plans to remain as chairman of the Appropriations subcommittee on defense.

Sen. Arlen Specter (R-Pa.), who is in line to succeed Sen. Orrin G. Hatch (R-Utah) as Judiciary chairman, is the senior member of the moderate faction within the largely conservative Senate GOP. Hatch is more conservative. But Specter has supported the Republican majority on the committee in approving even the most controversial of President Bush's judicial nominations, and aides to conservative senators said they do not expect a challenge to Specter's ascension -- at least not so far.

The Judiciary Committee will be especially important in the next Congress if, as many expect, the president will be making one or more nominations to the Supreme Court. Republicans, angry at Democratic filibusters that have blocked some circuit court nominees, are vowing a new effort next year to ban filibusters on judicial nominations.

Most important, Senate Republicans appear to have headed off a potentially divisive fight for the top GOP post in 2006 when Frist, abiding by his two-term pledge when he first ran for the Senate in 1994, is expected to retire. Frist has not said definitively that he will leave, but colleagues believe he will do so.

After testing the waters for several months about his chances of succeeding Frist, Santorum, third-ranking in the GOP pecking order and a leader of the party's most militant conservatives, let it be known last week that he would most likely run for the second-ranking job of party whip.

That appears to clear the way for Sen. Mitch McConnell (R-Ky.), the current whip, to run unopposed for the No. 1 post. Many senators have said they believe McConnell had more than enough votes to win, even before Santorum bowed out, but they appeared relieved to be spared a potentially bloody showdown. McConnell is conservative but is not drawn to ideological combat to the same degree that Santorum is.

Responding to the term-limit movement during the 1990s, Republicans imposed six-year limits on committee chairmanships and leadership posts below that of party leader. The limits started taking effect for leadership jobs last year, but this is the first year they will affect committee posts, which are otherwise governed by seniority.

In addition to the Appropriations and Judiciary changes, McCain will step down as chairman of the Commerce, Science and Transportation Committee. Stevens will succeed him as chairman of the panel. McCain could take the helm of the Indian Affairs Committee for two years, after which he would be in line for the Armed Services chairmanship. Sen. Ben Nighthorse Campbell (R-Colo.), currently Indian Affairs chairman, is retiring this year.

The impending retirement of Sen. Don Nickles (R-Okla.) opens up the Budget chairmanship, which could be taken by Sen. Judd Gregg (R-N.H.) or Wayne Allard (R-Colo.). Gregg is chairman of the Health, Education, Labor and Pensions Committee. If Gregg switches to budget, Sen. Mike Enzi (R-Wyo.) would be in line to take over the Health Committee.

Chairmanship of the Intelligence Committee hinges in large part on possible reconstitution of the panel as part of the broader reorganization of intelligence operations under consideration by Congress. Depending on the outcome, Sen. Pat Roberts (R-Kan.) might continue as Intelligence chairman or take over as chairman of Agriculture, succeeding Cochran. If Roberts does not take the Agriculture chairmanship, freshman Sen. Saxby Chambliss (R-Ga.) is in line to assume the post. Hatch might also seek the Intelligence chairmanship, GOP sources said.

On the Democratic side, only one job is in question -- that of Minority Leader Thomas A. Daschle (S.D.), who is faces a stiff reelection challenge from former representative John Thune (R). Daschle is a shoo-in for another term as Democratic leader if he is reelected. But if he is defeated, Democratic Whip Harry M. Reid (Nev.) is his likely successor, according to many Democrats. Sen. Christopher J. Dodd (Conn.), who ran before for the top Democratic post, has not said whether he would do so again.

If Democrats take over the Senate, which Republicans control by a two-vote margin, most chairmen would be familiar faces: the same people who ran committees while Democrats controlled the Senate in late 2001 and 2002, including Sens. Robert C. Byrd (W.Va.) at Appropriations, Patrick J. Leahy (Vt.) at Judiciary and Kent Conrad (N.D.) at Budget. Sen. Daniel K. Inouye (Hawaii) is in line to succeed retiring Sen. Ernest F. Hollings (S.C.) at Commerce.