Senator Arlen Specter‘s switch to the Democratic party is obviously an enormous boon to President Barack Obama‘s legislative agenda. Presuming that Al Franken ‘s Minnesota Senate race victory will eventually be ratified, Specter’s vote will bring the Senate Democratic tally to 60, which will enable Dems to cold-cock any Republican filibusters that may arise in response to this or that legislative measure.

In a statement issued about 90 minutes ago, Specter said “he had concluded that his party had moved too far to the right, a fact demonstrated by the migration of 200,000 Pennsylvania Republicans to the Democratic Party,” says a N.Y. Times story that went up at 12:13 pm.

“‘I now find my political philosophy more in line with Democrats than Republicans,” Specter said, acknowledging that his decision was certain to disappoint colleagues and supporters.” Specter will run as a Democrat in the 2010 Pennsylvania Senate race, and of course there’s the matter of his health, which hasn’t been perfect. But as long as Specter is fit and voting and plugging away, this is great news for Team Obama.

“The news shocked Senate Republicans, who had been hanging on to their ability to block legislation by a thread,” the Times story said. “Senator Mitch McConnell of Kentucky, the Republican leader, called an emergency meeting of party leaders who had no forewarning of Specter’s plans.”