Holy crap:

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.“

This news is pretty earth-shattering from my perspective. CNN’s Dana Bash called the news “seismic.”

h/t Think Progress

Update: Here’s John Cole:

I’m still waiting on my Soros check and forty virgins, so don’t get too excited, Arlen. Oh, and by the way, wingnuts- how is that Republican purity treating you? Is the GOP small enough to drown in a bathtub yet? Going to love hearing how a loyal foot soldier for three decades in the GOP wasn’t “conservative enough.”

And on a serious note, I think this is how party switching should be done. At the end of the term and then run on the ticket with your new party, not right after an election. Additionally, the weirdest thing about being a Democrat is I don’t feel any different than I did when I was a Republican, other than that I no longer have to make excuses for crazy and stupid people.

Holy shit! We’re now at 60 Dems in the Senate (assuming Norm Coleman gives up before the heat death of the universe).