Democratic candidates defeated Republican incumbents in Alaska, New Hampshire, North Carolina, Oregon, and, after a lengthy recount process, Minnesota.

These elections marked the first time since 1964 in which a Democratic presidential candidate who won the White House had a Senate coattail effect.

As of 2024, this is the last time Democrats won U.S. Senate seats in Alaska, Arkansas, Iowa, Louisiana, North Carolina, and South Dakota.

Not on the ballot, but running a write-in campaign, was Darryl W. Perry, the 2004 Libertarian Party nominee for Pennsylvania State Treasurer and 2007 candidate for Mayor of Birmingham, Alabama.

[16] Sessions defeated Figures, taking 63% of the vote to Figures's 37% Ted Stevens Republican Mark Begich Democratic Dispelling rumors that he would retire due to advanced age (he was 84 years old on election day) and ongoing federal investigations into his conduct, senator Ted Stevens filed papers for re-election for an eighth term.

On April 1, 2009, U.S. Attorney General Eric Holder, citing serious prosecutorial misconduct during the trial, decided to drop all charges against Stevens—an action that vacated his conviction.

The Democratic nominee was 2nd district Congressman Mark Udall of Boulder who announced on January 15, 2007, that he would seek the seat and did not draw significant primary opposition.

In 1988 and 2000, the Democratic vice presidential nominees Lloyd Bentsen and Joe Lieberman, ran similarly for their seat in Texas and Connecticut, respectively.

On November 24, 2008, Governor Minner appointed Biden's longtime Chief of Staff Ted Kaufman to fill the seat.

[52] The announcement followed by just six days the disclosure that he had pleaded guilty on August 1, 2007, to a reduced misdemeanor charge arising out of his arrest on June 11 at the Minneapolis airport for soliciting sex with a man in the restroom.

[59] Chad Koppie, a retired airline pilot and vice-chairman of the Illinois Center Right Coalition, was the nominee of the Constitution Party.

Once thought to be secure in his re-election, McConnell's lead had shrunk dramatically thanks to the financial crisis and polling showed the race tightening between him and Lunsford.

Since those elections, Democrats have had to endure the loss of some reliable voters because Hurricane Katrina dispersed many African-Americans from New Orleans, although the vast majority still live within Louisiana.

On November 29, after being personally recruited by Vitter and former Bush administration official Karl Rove, Kennedy announced plans to challenge Landrieu in 2008.

[71] Republican author and conservative activist Jerome Corsi, known for his public criticism of Kerry, had stated that he would run for the seat in 2008 but later changed his mind.

Jim Ogonowski, a retired Air Force pilot who was closely defeated by now-Representative Niki Tsongas in a 2007 special election, was running against Kerry.

These factors, coupled with a national political climate favorable to Democrats, made the Minnesota Senate race one of the most competitive and closely watched of the cycle.

[89] On January 3, 2009, with the recount apparently completed, Franken had an unofficial lead of 225 votes, but former senator Coleman's attorneys contested the official results in the courts.

As a result, Mississippi's Attorney General Jim Hood challenged Barbour in court, claiming that the special election needed to be held within 100 days of Lott's resignation, as per state law.

[99] However, Barbour filed an appeal to the Mississippi Supreme Court, which overturned the earlier ruling and set the special election for November 4, 2008.

Former Governor Mike Johanns, who recently resigned as Agriculture Secretary, was the Republican nominee, having defeated opponent Pat Flynn 87–13 in the primary.

Scott Kleeb, 2006 candidate for Nebraska's 3rd congressional district, defeated businessman Tony Raimondo, a former Republican, by a wide margin in the Democratic primary.

[120] Domenici normally would have been expected to win re-election easily, having won his current term with the support of two out of three New Mexico voters; however, he was to be investigated by the Senate Ethics Committee for his role in firing U.S. Attorney David Iglesias.

Domenici's role in the developing scandal had reduced the probability he would have been re-elected, and a SurveyUSA poll showed his approval ratings at 41%, with 54% disapproving.

A Rasmussen poll released May 11, 2008, showed Hagan leading Dole by a statistically insignificant margin, 48% - 47%,[128] suggesting a competitive race.

Smith faced Democratic Oregon House of Representatives Speaker Jeff Merkley in the November general election.

[143] Conley, whose victory in the Democratic primary over Michael Cone was a surprise, is a former Republican who supported Ron Paul in 2008 and campaigned as the more conservative candidate on some issues, notably illegal immigration and the bailout of Wall Street.

[147] According to a November 2006 SurveyUSA poll, Johnson had an approval rating of 70%, with just 26% disapproving of his performance,[148] making him an early favorite despite the state's Republican lean.

[157] Texas House of Representatives member and Afghanistan War veteran Rick Noriega secured his place as Cornyn's Democratic challenger in the March 4 primary, beating out opponents Gene Kelly, Ray McMurrey, and Rhett Smith.

[175] In the primary on August 19, Goodenough was defeated by a political newcomer, Gillette defense attorney Nick Carter, who became Barrasso's opponent in the general election.