Pennsylvania Senator Arlen Specter was never quite a darling of the right, but his abandonment of the Republican Party—announced today—does more than raise the ire an already struggling conservative political machine.

The 80-year-old Specter was seen as one of the last moderate Republicans. Resisting partisan politics, he voted for the stimulus bill which spurred former Republican congressman Pat Toomey to announce an electoral challenge to Mr. Specter in 2010. An early poll favors Mr. Toomey.

Critically, Specter's hop across the aisle brings the Democrats in the Senate to a filibuster-proof 60 which could provide a fast track for any piece of legislation favored by the Democrats.

Professor of Political Science at the University of Pennsylvania Rogers Smith characterizes Specter's decision as "the last nail in the coffin for moderate northeastern Republicans getting pushed out of the Republican party" and says Specter likely saw a far more of a viable political future for himself with the Democrats.

When he spoke to Big Think--back during the Bush years--Specter did not signal second thoughts about the GOP per se but he did acknowledge a certain ill wisdom in wiretapping, calling the ruling's overturn correcting "the injustices of the past." Watch the video here.