The Republican Party is now on suicide watch:

Pennsylvania Sen. Arlen Specter will switch his party affiliation from Republican to Democrat and announced today that he will run in 2010 as a Democrat, according to a statement he released this morning.

Specter's decision would give Democrats a 60 seat filibuster proof majority in the Senate assuming Democrat Al Franken is eventually sworn in as the next Senator from Minnesota. (Former Sen. Norm Coleman is appealing Franken's victory in the state Supreme Court.)

"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."

He added: "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."

MSNBC's David Shuster, in the video above, relayed the information that Specter reached the decision because he realized that his vote for the stimulus package had irrevocably breached his relationship with the increasingly wingnutty Republican base, and that he was no longer willing to submit himself to the judgment of that base in the GOP primary. Smart move.

Of course, now that he's a Democrat, don't expect any miracles. Reportedly, he still intends to vote against cloture on the Employee Free Choice Act ...

UPDATE: Here's Specter's statement:

When I supported the stimulus package, I knew that it would not be popular with the Republican Party. But, I saw the stimulus as necessary to lessen the risk of a far more serious recession than we are now experiencing.

Since then, I have traveled the State, talked to Republican leaders and office-holders and my supporters and I have carefully examined public opinion. It has become clear to me that the stimulus vote caused a schism which makes our differences irreconcilable. On this state of the record, I am unwilling to have my twenty-nine year Senate record judged by the Pennsylvania Republican primary electorate. I have not represented the Republican Party. I have represented the people of Pennsylvania.

I have decided to run for re-election in 2010 in the Democratic primary.