Expected Democratic gains in the election raise the possibility that the Senate, for the second time in six years, will end up in a 50-50 tie.
If that happens, Democrats would like to revive a power-sharing deal that was struck in 2001. But partisan passions on Capitol Hill are stronger now than when President Bush took office promising to be "a uniter, not a divider."
Republicans would officially still be the majority party in an evenly divided Senate because Vice President Dick Cheney, in his role as president of the Senate, would give the GOP a tie-breaking vote. But Democrats would surely demand a greater role in determining how the Senate treated Bush's legislative agenda in his final two years in the White House.
Control of Congress
Currently Republicans hold 55 seats and the Democrats 44. Sen. James Jeffords, an independent from Vermont who usually votes with the Democrats, is retiring at the end of this session.
The 2000 election resulted in a Senate split down the middle. Democratic leader Tom Daschle of South Dakota became majority leader for just 17 days, between Jan. 3, 2001, when the new Senate was sworn in and Al Gore was still vice president, and the Jan. 20 inauguration of Bush and Cheney.
In returning to the majority leader position, Sen. Trent Lott, R-Miss., negotiated with Daschle a power-sharing arrangement under which the two parties got equal numbers of seats and staff positions on committees. Republicans chose committee chairmen and controlled the agenda on the Senate floor.
Lott took some heat from his Republican colleagues at the time for being overly generous to Democrats, but it paid off four months later when Jeffords bolted from the GOP and became an independent allied with the Democrats. That put the Democrats back in control with Daschle as majority leader.
The Lott-Daschle deal stayed intact until November 2002, when Republican James Talent defeated Missouri's appointed senator, Jean Carnahan, in a special election and Republicans regained power. They've held majorities on Senate committees since then.
This time, Democrats may need the help of two independents to reach parity with the Republicans.
Independent politics
Rep. Bernie Sanders, another Vermont independent, is the front-runner in the race to succeed Jeffords. Sanders has always been a member of the Democratic caucus in the House and his office said he would continue to support the Democrats in the Senate.
Democratic Sen. Joe Lieberman of Connecticut appears likely to return to Congress as an independent after his loss to a Democratic challenger in the primaries. Lieberman, in line to become chairman of the Homeland Security and Governmental Affairs Committee if Democrats capture the Senate, is also committed to staying with the Democratic caucus, his office said.
Jim Manley, press spokesman for Senate Democratic leader Harry Reid of Nevada, said that in the event of a 50-50 breakdown the 2001 Lott-Daschle deal "should serve as a useful guidepost for any negotiations" on power-sharing between Reid and Sen. Mitch McConnell, R-Ky.
Politics of partisanism
But McConnell, the favorite to succeed retiring Sen. Bill Frist, R-Tenn., as Republican leader, and Reid would be negotiating in a far more partisan atmosphere than in 2001, when the new president and the Democrats were talking of cooperation and the idea of senatorial harmony wasn't quite so unattainable.
Much longer ago, the Senate was also deadlocked at 38-38 in 1881 when Republicans, in control of the White House, won the allegiance of a wavering independent by promising him the Agriculture Committee chairmanship. Republicans took over control of the major committees, while Democrats took advantage of GOP disarray to hold onto staff positions such as sergeant at arms and secretary of the Senate.
State legislatures have at times found more congenial ways to deal with ties. The Indiana House in 1988 created co-speakers who presided on alternate days. The Wyoming Senate in 1974 resolved a tie by flipping a coin.