The 2010 United States Senate election in Pennsylvania took place on November 2, 2010, during the 2010 midterm elections. Incumbent Republican-turned-Democrat U.S. Senator Arlen Specter ran for reelection to a sixth term, but lost in the Democratic primary to Joe Sestak. Republican nominee Pat Toomey then won the seat.
Toomey had previously run for United States Senate in 2004, challenging Specter for the Republican nomination, but was narrowly defeated in the primary. Specter went on to be reelected to his fifth term, defeating the Democratic nominee, Congressman Joe Hoeffel. Toomey announced on April 15, 2009, that he would again seek the Republican nomination for U.S. Senate in the 2010 election.
The primary season was marked by Specter's decision in early 2009 to switch from the Republican Party to the Democratic Party due to his disagreement with the increasingly conservative positions of the party, pitting him against Sestak in the Democratic primary. The contest, characterized by attacks between the two Democratic candidates, was one of the most-watched primary races of the 2010 election cycle. Sestak ultimately defeated Specter in the May 18 primary, garnering 53.9% of the vote, to Specter's 46.1%. Pat Toomey easily defeated challenger Peg Luksik for the Republican nomination. Toomey received 81.5% of the vote, to Luksik's 18.5%.
Toomey defeated Sestak in the general election on November 2, 2010. Toomey garnered 2,028,945 votes (51.01%) to Sestak's 1,948,716 (48.99%), a margin of 80,229 votes (2.02%). The race was called by the Associated Press shortly before midnight. Not long thereafter, Sestak officially conceded the election to Toomey. Toomey's winning margin made this election the third-closest race of the 2010 Senate election cycle, behind only the elections in Illinois and Colorado. As of 2022, this is the last time that Lehigh County and Monroe County voted for a Republican.
Democratic primary
Candidates
Joe Sestak, U.S. Congressman
Arlen Specter, Incumbent U.S. Senator
William C. Kortz, Member of Pennsylvania House of Representatives (withdrawn candidacy)
Campaign
The Democratic party race between Specter and Sestak was considered one of the most bitter and highly watched of all the 2010 primary elections. On April 28, 2009, Specter switched to the Democratic Party after having served in the Senate as a Republican for 28 years, encouraged by Vice President Joe Biden and Pennsylvania Governor Ed Rendell, after he had voted in favor of President Barack Obama's economic stimulus plan and was faced with opposition from Pennsylvania Republicans. Although Specter claimed he switched largely because he disagreed with the increasingly conservative direction the Republican Party was heading in, he also admitted that the switch was due to his poor chances of winning a Republican primary against Toomey due to Specter's support of the Obama stimulus package . The Democratic establishment had till then encouraged Sestak, a former U.S. Navy admiral and the representative of Pennsylvania's 7th congressional district, to run in the Democratic primary. But after Specter switched parties he was largely embraced by such major Democratic figures as Obama, Biden, Rendell and Senate Majority Leader Harry Reid. The Democratic establishment now feared Sestak would harm Specter's chances in the general election and encouraged him to drop out, but Sestak refused and strongly criticized Specter's party switch as an opportunistic move aimed solely at political self-preservation.