United States Senate Democratic primary election in Pennsylvania, 2010

United States Senate Democratic primary in Pennsylvania, 2010

2004 ← May 18, 2010 → 2016

Nominee Joe Sestak Arlen Specter Party Democratic Democratic Popular vote 568,563 487,217 Percentage 53.8% 46.2%

County results key:   Joe Sestak   Arlen Specter

The Democratic primary for the 2010 United States Senate election in Pennsylvania took place on May 18, 2010, when Congressman Joe Sestak defeated incumbent Arlen Specter, which led to the end of Specter's five-term Senatorial career. Just prior to the start of the primary campaign, after serving in the Senate as a Republican for 29 years, Specter had switched to the Democratic Party in anticipation of a difficult primary challenge by Pat Toomey; Sestak was ultimately defeated by Toomey in the general election. Political observers and journalists described the race between Specter and Sestak as one of the bitterest and most watched of all the 2010 primary elections.

Although Sestak was initially urged to run by the Democratic establishment, Specter gained wide support from Democrats after he switched parties. Major political figures like President Barack Obama and Pennsylvania Governor Ed Rendell later tried to sway Sestak from continuing the race, fearing he would damage Specter's chances in the general election. Former President Bill Clinton offered Sestak a position in the Obama administration if he withdrew his candidacy, an offer Republicans would later criticize. Sestak refused to drop out and criticized Specter's party switch as an opportunistic move aimed solely at self-preservation. Nevertheless, Sestak struggled to overcome problems stemming from low name recognition and Specter's support from such individuals as Joe Biden and Harry Reid, and organizations like the AFL-CIO and Pennsylvania Democratic Committee.