Elections to the United States Senate will be held on November 7, 2006, with 33 of the 100 seats in the Senate being contested. Since Senators are elected for six-year terms, those elected will serve from January 3, 2007 until January 3, 2013. Those Senators who were elected in 2000 will be seeking re-election (or retiring) in 2006.

The U.S. House election, 2006 is scheduled for the same date as the Senate election, as well as many state and local elections including those for 36 state governors.

The Senate is currently composed of 55 Republicans, who have been in the majority since 2002, 44 Democrats, and 1 independent. (The independent, Jim Jeffords of Vermont, is allied with the Democratic caucus and has voted with Democrats to give them the majority in the past.) The Democrats will need to pick up 6 seats to retake control of the Senate. (Should the Democrats gain 5 seats, the Republicans will retain control of the body because of the affiliation of the Vice President, Dick Cheney.) The Republicans will need to pick up 5 seats to obtain a "working majority", or 60 members (the amount needed to break a filibuster). Of the seats up for election, 15 are held by Republicans, 17 by Democrats, and 1 by the sole independent.

It is not yet clear which seats will have the most competitive races. Past election history indicates that incumbents are difficult to defeat, even when their party affiliation is at odds with the natural tendencies of the state, and that the most competitive races are those where the incumbent retires, followed by those in which the incumbent has served only one term. Beside the elections listed below, it is possible that additional special elections will be held due to the death or resignation of Senators in the interim. This would also change the party balances listed above.

• George Allen (R-VA) – Allen is a popular Senator, but if he faces popular Governor Mark Warner, this race would be very competitive.

• Daniel Akaka (D-HI) – The second-oldest member of the Senate facing reelection, after Robert Byrd (below), Akaka will be 82 years old if sworn into office for a third complete term. Though he has not yet announced whether he will retire or seek reelection, many consider Senator Akaka to be among the most likely to retire in this election cycle.

• Robert Byrd (D-WV) – Byrd's 89th birthday will occur less than two weeks after the election, making him – by nearly seven years – the oldest senator facing the expiration of their term. If he chooses to retire, or his age or health should become a substantive issue, a Republican challenger would likely have a strong possibility of gaining a seat in a state won by President Bush in 2004 by nearly 13 points. It should be noted, though, that West Virginia elected a Democratic governor in 2004 with over 60% of the vote, as well as electing Byrd and junior senator Jay Rockefeller with substantial margins in 2000 and 2002 respectively.

• Lincoln Chafee (R-RI) – Chafee, perhaps the most liberal Republican remaining in the Senate, could face a primary challenge from more conservative members of his own party who label him as a Republican in name only. He could also face a strong Democratic challenger. Chafee is popular in Rhode Island, but a slightly weaker candidate could still defeat him due to Rhode Island's heavy Democratic tilt.

• Hillary Clinton (D-NY) – Former First Lady Clinton was elected in 2000 in this traditionally blue state with 55% of the vote, but she was helped by facing Rick Lazio, who was seen as a fill-in for former New York City mayor Rudolph Giuliani. Republican hopes for this seat rest upon recruiting a strong candidate, such as Giuliani or Governor George Pataki, and using how controversial and polarizing Hillary Clinton is to gain an advantage. This could also make or break the potential presidential campaigns of Clinton, Giuliani, and Pataki. Republican Representative Vito Fossella has also tried to recruit Colin Powell to run against Clinton.

• Jon Corzine (D-NJ) – Corzine, currently the most popular elected official in New Jersey, would probably be easily reelected if he ran. However, Corzine has announced his candidacy for the 2005 gubernatorial election. If he wins, another Democrat will be appointed to his Senate seat. That Democrat may be more vulnerable, since he or she will only have held the office for a year before the 2006 election and could face a tough challenge if a popular candidate, possibly the failed Republican candidate for governor, runs for Senate.

• Mark Dayton (D-MN) – The Minnesota freshman became national news when he chose to close his Capitol Hill office three weeks before the 2004 election, citing a possible terrorist threat. Government officials denied having issued any terror warning, and no other Senator closed his office. Combined with what is perceived as a lackluster record in the Senate, this could make Dayton vulnerable in 2006. Governor Tim Pawlenty is a possible challenger, as is Rep. Mark Kennedy.

• Dianne Feinstein (D-CA) – Feinstein, highly popular in the state, has long harbored ambitions of becoming Governor of California – she narrowly lost the 1990 gubernatorial election to Pete Wilson – and a race against Arnold Schwarzenegger would certainly be competitive. If Feinstein runs for Governor, the Senate race would be wide open and extremely competitive. If Feinstein seeks to remain in the Senate, her seat would be considered safe.

• Bill Frist (R-TN) – Frist has previously promised to leave the Senate when his second term ends in 2006. The current Tennessee governor is Democrat Phil Bredesen, raising the possibility that either of the two could run for the other's office, as the elections will be held simultaneously. However, Frist has hinted at retiring to prepare for a presidential bid, and is widely expected to do so. Another possible Democratic candidate is Representative Harold Ford, Jr.. This may or may not be a competitive race as an open seat.

• Jim Jeffords (I-VT) – Jeffords left the Republican Party to become independent soon after being elected as a Republican in 2000. If he runs again, it is unclear whether he will run as an Independent or a Democrat. His reelection may depend on whether he faces a Democratic challenger as well as a Republican one. As he caucuses with the Democrats, the Democratic party might attempt to dissuade or forbid challenges. Jeffords' situation is very similar to that of Vermont Representative Bernie Sanders (I-VT), though Sanders has always been independent.

• Trent Lott (R-MS) – The former Senate Majority Leader, Lott stepped down from that post in 2002 due to controversial remarks he made at a private event regarding former Senator Strom Thurmond and the Dixiecrat Party. It is as yet unknown whether Lott will attempt reelection, and whether the state's conservative voting pattern will be able to carry him to reelection in light of the controversy.

• Ben Nelson (D-NE) – Nelson, one of the most conservative Democrats in the Senate, is running for re-election in a state that went for George W. Bush by 35 percentage points. Mike Johanns, the Secretary of Agriculture and former governor, would still presumably be a serious candidate despite his holding a Cabinet post. If Johanns were to run, he has the option of resigning from his post first, as Mel Martinez did in Florida.

• Bill Nelson (D-FL) – As the only southern Democrat facing re-election, Nelson might draw major regional attention to this race. Florida also will elect a new governor in 2006, and the cost of two major campaigns in a large state could require that one of the Republican candidates have a high profile. One such candidate would be current governor Jeb Bush, who is barred by term limits from seeking re-election and could conceivably seek the Senate seat.

• Jim Talent (R-MO) – Talent, who was elected to the four remaining years of this term in a 2002 special election, might face a strong Democratic challenge for his seat. Unlike most states, Missouri will not hold an election for governor in 2006, making this the only statewide race in a traditional battleground state.

• U.S. Senate election, 2004
• U.S. Senate election, 2008
• U.S. House election, 2006