Washington (CNN) - Sen. Arlen Specter's party switch last year was a boon for Democrats, and maybe a survival move on his part. But with the wave of anti-incumbency sweeping the nation, his job is still in jeopardy.
Terry Madonna of Franklin and Marshall University's Center for Politics and Public Affairs is following the Democratic primary between Specter and suburban Philadelphia Rep. Joe Sestak.
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"This has turned into a dogfight," Madonna said, pointing to polls that indicate support for Sestak is surging in the weeks leading up to Tuesday's statewide vote, in which only Democrats can participate.
Specter's switch from Republican to Democrat, was by his own admission made in part to aid his chances for re-election, a fact Sestak has been all too happy to point out.
In an effort to keep the seat in Democratic hands, President Obama has come down squarely behind Specter, speaking out in support of the five-term veteran.
By comparison, "the voters don't consider [Sestak] to be a career politician in quite the same way," Madonna notes, since Sestak is only in his second term.
Sestak has been a "staunch supporter" of the Obama agenda, and has steered clear of criticizing the president for backing Specter.
The winner of the Democratic primary will face former three-term Republican Congressman Pat Toomey in the general election.
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