Louisiana Sens. Mary Landrieu (D) and David Vitter (R) are archrivals who barely speak.

But they could have to work alongside each other as chairwoman and ranking member of the Small Business Committee in the 112th Congress, one of the more entertaining possible outcomes of a chamber-wide committee shuffle that will take place early next year.

With five committee chairmen and ranking members retiring next year, plus two locked in tight re-election battles and Energy and Natural Resources ranking member Sen. Lisa Murkowski (R-Alaska) having lost her primary, the lineup on major committees could change dramatically in January.

The Vitter/Landrieu scenario begins with Sen. Kit Bond, the top Republican on the Senate Intelligence Committee. Bond is retiring, creating an opening for Olympia Snowe to leave her spot as ranking member on Small Business to take over the Intelligence slot.

That would leave Vitter in line to ascend to the top GOP spot on Small Business, making the Louisianans the first pair from the same state to head a committee since New Mexico Sens. Pete Domenici (R) and Jeff Bingaman (D) led the Energy and Natural Resources panel from 2003 to 2008.

While Landrieu has enjoyed a cordial relationship with the moderate Snowe, she and Vitter have one of the uglier rivalries in the Senate, which could stoke partisan wrangling from the typically low-key Small Business dais next year.

Neither Senator would comment for this story, and others in line for top committee post also chose to stay mum.

Snowe has an opportunity at Intelligence because Sen. Orrin Hatch (R-Utah), who outranks her on that panel, is scheduled to become the ranking member of Finance.

When Arlen Specter (D-Pa.) switched parties last year, Sen. Jeff Sessions (R-Ala.) temporarily took Specter’s spot as the ranking member of the Judiciary Committee. Under an agreement reached last spring, that spot will go to Finance ranking member Sen. Chuck Grassley (R-Iowa) in the 112th Congress, making the Iowan’s perch on Finance available for Hatch, who is without a senior post on any committee despite his lengthy service in the Senate.

That complex arrangement could be thrown out entirely if Republicans were to win back the Senate, since the agreement was reached with the assumption that the GOP would be the minority party next year.

[IMGCAP(1)]The retirements of Budget ranking member Judd Gregg (R-N.H.) and Rules ranking member Bob Bennett (R-Utah) will also set off a domino effect among Republicans on those panels next year. And if Murkowski does not return to the Senate as a write-in candidate, the top GOP spot on Energy will also be available.

Meanwhile, several Democratic chairmen are in tight re-election races. If any of them lose, it would set up a cascade of committee moves.

For example, Sen. Blanche Lincoln (D-Ark.) has tried to leverage her assignment as chairwoman of the Agriculture Committee as an advantage in her re-election campaign, but she has consistently been behind GOP challenger Rep. John Boozman in the polls. If she loses, the three Democrats in line behind her ­— Tom Harkin (Iowa), Patrick Leahy (Vt.) and Kent Conrad (N.D.) ­— all chair top committees, meaning the door may be open for Debbie Stabenow (Mich.) to take over Agriculture.

Like Lincoln, Environment and Public Works Chairman Barbara Boxer (D-Calif.) is facing a tough re-election campaign, and a Democratic loss in California could create another opening that could be filled by Sen. Tom Carper (D-Del.), who does not have a chairmanship.

Sen. Tim Johnson (D-S.D.) is poised to take over for Banking, Housing and Urban Affairs Chairman Chris Dodd (D-Conn.), who is retiring. There was speculation last year that Johnson, who is still recovering from a brain aneurysm that occurred December 2006, might be too frail for the chairmanship, but a challenge from a less senior Member, such as Sen. Jack Reed (D-R.I.), appears unlikely. Johnson is also up for re-election in 2014, and aides said it will be to his electoral advantage in his GOP-leaning state to campaign as the chairman of a powerful Senate committee.

Johnson’s neighbor to the north, Sen. Byron Dorgan (D-N.D.), is also retiring this year, creating an opening for the Indian Affairs chairmanship, which could be Sen. Maria Cantwell’s for the taking. Members ahead of the Washington Democrat on that committee already hold prestigious chairmanships they are unlikely to forfeit, but even Cantwell may take a pass because a chairmanship at Indian Affairs could require her to drop her assignment on either the Commerce or Finance committees. She might be unwilling to give up either prestigious spot, but one could decide it is in her interest to do so since she will be up for re-election next year.

“At a time when gridlock pervades Washington and nothing seems to get done, a Member’s ability to deliver for their state via the clout that comes with a chairmanship can go a very long way,” one Democratic strategist said.

Some of these committee shuffles could be contentious, but the transition is usually smoother in the Senate than in the House.

“Traditionally in the Senate, the chairmanship goes to Member with the most seniority on the committee, though every couple of Congresses you will hear grumbling from some Members that they want to give someone else a shot at running the committee,” said Marty Paone, a former Democratic leadership aide who now works for Prime Policy Group. “Such talk often comes from former House Members, especially if there’s discussions in the press of possible changes in House chairmanships, which sometimes are determined by other factors, such as party loyalty.”

But with control of the chamber still in play in November, neither Democrats nor Republicans are interested in publicly speculating on committee slots that might change hands next year.

“Sen. Landrieu isn’t focused on speculation about what may happen in the next Congress,” Landrieu spokesman Aaron Saunders said. “Her energy and attention is devoted entirely to passing the Small Business Jobs Creation Act and getting America’s small businesses the help they need as soon as possible.”

And Republicans maintain they are focused on Election Day only and are not allowing Members to focus on any committee posts until after November.

“It’s sort of a back-burner issue at this point,” one GOP aide said.