Sen. Arlen Specter lost his bid for a sixth term, succumbing in the Democratic primary to relative newcomer Joe Sestak, a two-term congressman who successfully campaigned against Specter's recent party switch.
Specter's loss represents the biggest rebuke of incumbent lawmakers so far this year. Longtime Rep. Alan Mollohan, D-W.Va., lost his primary last week and Sen. Bob Bennett, R-Utah, was rejected for the GOP ballot by his own party 10 days ago.
Political pundits had warned that Specter needed high turnout in Philadelphia and its suburbs in order to win, but Tuesday's cold rain helped to lower even further he traditionally low primary turnout in the region.
"Philadelphia generally does not vote as strongly as the rest of the state in primaries to begin with," said Joseph McLaughlin, director of the Institute for Public Affairs at Temple University in Philadelphia. "And coupled with the rain -- rain is not good for Arlen Specter."
Specter lost his bid despite substantial help from the Democratic Party, which promised to aide in his re-election effort when he switched parties. Specter became a Democrat last year, giving Senate Democrats the 60 critical votes they needed to pass legislation without the threat of a GOP filibuster. But even with help from President Obama, who cut a television ad praising Specter, and Vice President Biden, who campaigned in person, Specter was unable to survive politically.
Many voters complained that Specter's switch appeared too self-serving, a notion reinforced by a powerful television advertisement paid for by Sestak that shows Specter admitting he changed parties to save his own job.
"I think the party switch certainly didn't help him, particularly in a time when the public is suspicious of those who are in office as to whose interests they are looking out for," McLaughlin said. "The ad by Sestak was devastating and probably the single most important factor in his defeat."
Others voters said they believed Specter's five terms were enough and it was time for a change.
Sestak eagerly campaigned as someone who represented that change, even though he has served in Congress for nearly four years and has voted much like Specter for the past year.
Sestak often referred to Washington as "broken" and that Specter was ill-equipped to fix it, especially as a recent party switcher.
Jim Broussard, professor of history at Lebanon Valley College in Annville, said Specter's loss was less an indictment of incumbents and more likely, "another example of the general rule that party switchers do not do very well in their new party when they come up for election."
Sestak will have to face conservative Republican candidate Pat Toomey in the general election. Toomey handily won the GOP primary, earning more than three times the votes as conservative activist Peg Luksik. Polls have shown Sestak faring better than Specter against Toomey in a general election lineup.
In Arkansas, Democratic Sen. Blanche Lincoln was running comfortably ahead of liberal challenger Lt. Gov. Bill Halter, with hopes of avoiding a June runoff by winning 50 percent of the vote in a three-way primary. Rep. John Boozman was ahead in his eight-way Republican primary, and looked likely to avoid a runoff.
Polls have shown Boozman beating Lincoln by as much as 18 points.