2008 US Senate Elections

The 2008 United States Senate elections were held on November 4, 2008, with 35 of the 100 seats in the Senate being contested. Thirty-three seats were up for regular elections; the winners were eligible to serve six-year terms from January 3, 2009 to January 3, 2015, as members of Class 2. There were also two special elections, the winners of those seats would finish the terms that ended January 3, 2013.

The presidential election, which was won by Democrat Barack Obama, elections for all House of Representatives seats; elections for several gubernatorial elections; and many state and local elections occurred on the same date.

Going into these elections, the Senate consisted of 49 Democrats, 49 Republicans, and two Independents who caucused with the Democrats, giving the Democratic caucus the slightest 51–49 majority. Of the seats up for election in 2008, 23 were held by Republicans and 12 by Democrats. The Republicans, who openly conceded early on that they wouldn't be able to regain the majority in this election, lost eight seats. Democratic candidates defeated Republican incumbents in Alaska; New Hampshire; North Carolina; Oregon; and, after a lengthy recount process, Minnesota. Additionally, they won Republican-held open seats in Colorado, New Mexico, and Virginia. This election was the second cycle in a row in which no seats switched from Democratic to Republican, and the first since 1990 in which the Democrats retained all their seats. In addition, this was the largest Democratic Senate gain since 1986, where they also won eight seats. These elections marked the first time since 1964 in which a Democratic presidential candidate who won the White House had a Senate coattail effect.

Democrats held at least 57 seats as a result of the election. When the new senators were first sworn in, the balance was 58–41 in favor of the Democrats, with the unresolved election in Minnesota causing that seat to remain vacant. The April 2009 party switch of Pennsylvania senator Arlen Specter from Republican to Democrat and the July 2009 resolution of the Minnesota election in favor of Democrat Al Franken increased the Democratic majority to 60–40 (providing the Democrats, including the two Independent senators who caucus with them, a supermajority and thus able to hypothetically over-ride any filibusters). Republicans gained a seat in a January 2010 special election in Massachusetts, thereby making the balance 59–41 before the start of the next election cycle.

As of 2022, this is the last time Democrats won U.S. Senate seats in Alaska, Arkansas, Iowa, Louisiana, North Carolina, and South Dakota. This is the only time since 1990 that Democrats gained Senate seats in consecutive elections, and only one of two times since 1992 that either party has done so.