Sen. Arlen Specter (R-Penn.) is becoming a Democrat.

"I have decided to run for re-election in 2010 in the Democratic primary," said Specter in a statement. "I am ready, willing and anxious to take on all comers and have my candidacy for re-election determined in a general election."

"Since my election in 1980, as part of the Reagan Big Tent, the Republican Party has moved far to the right. Last year, more than 200,000 Republicans in Pennsylvania changed their registration to become Democrats. I now find my political philosophy more in line with Democrats than Republicans."

The move will give Democrats a filibuster-proof 60 vote majority in the Senate, presuming Minnesota's Al Franken is eventually seated. However, in his statement Specter said his opposition to the Employee Free Choice Act — widely seen as a defense against a Republican primary challenge — will not change.

Polls had shown that, despite his shift on EFCA, Specter was on his way to losing his seat if he stayed in the GOP. A Rasmussen survey from last Friday had former U.S. Rep. Pat Toomey beating the Senator by 21 points in the primary.

Sources told the AP that an announcement could come later in the day — or Wednesday.

Vice President Joe Biden and Pennsylvania Gov. Ed Rendell have urged Specter to switch parties in the past.

President Obama called Specter Tuesday to say Democrats "are thrilled to have you."

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Toomey Has Huge Lead over Specter in Pennsylvania     Permalink

First one poll then another poll have shown Sen. Arlen Specter (R-PA) trailing former congressman Pat Toomey by double-digit margins. The Rasmussen poll published yesterday puts Toomey ahead 51% to 30%.

Specter's real problem was the Democratic presidential primary in 2008. With the battle between Hillary Clinton and Barack Obama still raging last April, hundreds of thousands of moderate Republicans in Pennsylvania switched registration to vote in the Democratic primary. Most of these people normally voted for Specter. Now they are officially Democrats. With a big primary looming on the Democratic side in 2010, probably most of them will remain Democrats to vote in the Democratic primary. Thus the center of gravity of what is left of the Pennsylvania Republican Party has moved far to the right—towards Toomey and away from Specter. Under far less favorable circumstances, Toomey came within 1.7% of beating Specter in the 2004 senatorial primary. Now with the wind at his back and Specter unpopular with the right wing of the Republican Party for his occasional roll call votes with the Democrats, Toomey has an excellent chance of winning the nomination. Unfortunately, he has almost no chance of winning the general election against any of the numerous Democrats trying for their party's nomination. He is simply far too conservative for a state Obama carried by 11 points. Thus a Toomey win in the primary means that Pennsylvania will very likely flip and give the Democrats their 60th seat in the Senate (assuming Franken is seated by January 2011).