Sen. Arlen Specter switched parties last spring because he was fed up with conservatives keeping score. Now it looks like Pennsylvania Democrats, scorecards in hand, are more than ready to end Specter’s career on Tuesday for failing to toe their line. They don’t seem to care about his “love” for President Obama, don’t trust his sudden conversion, and are perturbed about him calling a bunch of them Republicans.

With little concern for their party’s new 80-year-old incumbent, the Keystone State Left has slipped into a swoon in recent days for the mostly-unknown Rep. Joe Sestak, an aw-shucks, Kennedy-quoting former naval admiral from the Philly suburbs. According to recent polls, Sestak has surged, and looks poised to win, or come very close, in the primary.

Why so close so late? Well, for one, Sestak’s strategy seemingly mimics that of former Rep. Pat Toomey, who challenged, and nearly beat, Specter in the 2004 GOP Senate primary and was running strong in the 2010 GOP contest until the senior senator dropped out. Hammering Specter on his ratings from lefty groups, Sestak presents himself as a fresh voice who is an authentic liberal. Here’s his latest ad:

Whether or not Sestak pulls off the upset, he deserves a hat tip from conservatives for driving what should have been an easy, coasted primary for Specter — the White House and state machine back him — as far left as a duffer’s hook on the 18th hole.

Kim Strassel explains the consequences of Sestak’s ambitious maneuvers in today’s Wall Street Journal:

What do Joe Sestak, Bill Halter and Colleen Hanabusa have in common? The left loves them. This is yet another reason Democrats are in trouble this fall . . . In Pennsylvania, Mr. Specter was against the unpopular card check; thanks to Mr. Sestak he’s now for it . . . [Democratic primaries] are generating nominees who are embracing, or even going beyond, the president’s unpopular agenda. This is the feud that may have the bigger consequences for this fall’s midterms.

Strassel’s right. Read the rest here.