Specter has ‘strong incentive’ to leave the Republican Party.

With former Rep. Pat Toomey (R-PA), who currently heads the right-wing Club for Growth, announcing that he will challenge Sen. Arlen Specter (R-PA) in a primary battle for his Senate seat in 2010, The Hill is reporting that Specter now has a “strong incentive to abandon his party this year.” Specter barely beat Toomey in 2004 and 2010 looks to be a much tougher fight:

Pennsylvania political experts say that Specter would likely face a more difficult challenge in 2010 because the Republican primary electorate in Pennsylvania has become more conservative.

“I think he has a lot of problems,” said Terry Madonna, a professor of political science at Franklin and Marshall College in Lancaster, Pa. “I think this is the test of lifetime.”

Madonna estimated that between 150,000 to 200,000 centrist Republicans switched registration to the Democratic Party in the 2008 election cycle, leaving the remaining GOP electorate more conservative.

If Specter were to lose to Toomey in the primary, he would not be able to run as an independent under Pennsylvania election law.