You might have seen yesterday that Sen. Arlen Specter came out against ECFA, saying he’ll vote against cloture - which means proponents of the “card check” bill won’t have a filibuster-proof majority, and the bill probably won’t pass.

There was much speculation as to what Specter would do - he’s supported unions in the past - but, via TPMDC, a poll out yesterday suggests why Specter made up his mind as he did:

A new Quinnipiac poll in Pennsylvania shows just how much trouble Arlen Specter could have in his 2010 Republican primary. Against his 2004 challenger Pat Toomey, who is expected to run again this time, he’s stuck in the twenties.

The numbers: Toomey 41%, Specter 27%. Specter’s loss of his Republican base also leaves him with weak numbers for a general election, with only 31% against a generic Democrat’s 33%.

So this is obviously Specter attempting to shore up his bona fides, by selling unions down the river. Notes Josh Marshall:

But by turning so dramatically on labor, which is a particularly big deal in Pennsylvania, I’m curious whether he can really make it through in the general, given the wild level of kow-towing to the right he’ll need to do to secure the nomination.

What Specter needs to understand is that there is likely to be a concerted effort both from the right and the left if he continues down this path. Strange bedfellows and all that - I could even see an alliance of sort between the Toomey contingent and Democrats to wound Specter, to undermine him prior to the primary, which would allow Toomey to win that primary so long as Specter runs as a Republican. Which I’m beginning to think he will, despite his noises about possibly mounting an independent run.

In other words, in trying to secure his right flank, Specter really will lose his left flank, especially if these poll numbers don’t improve. There might have been a time Democrats would have been happy to merely sit back with a tub of popcorn and watch the political bloodbath that will be the Specter-Toomey duel. The more stuff like this Specter does - the greater the chance that this audience will get in the game.