The first poll that doesn’t have Arlen Specter in the lead in the Pennsylvania Democratic Senate primary race is out today. The daily tracking poll by Muhlenberg College shows him tied with Joe Sestak.

Perhaps the Swift Boat ad has turned off voters. Or it might be that Sestak’s own devastating ad (reminding Democratic voters that George W. Bush declared, with Specter at his side in the 2004 Senate race, “I can count on this man”) has sunk in. And frankly, Specter is the quintessential Washington insider — there for decades, finger to the wind — who voters are none too enamored of these days.

Should Sestak prevail in the primary, it will set up quite a battle with Pat Toomey. Domestic issues will surely dominate. But here’s a race in which the left’s foreign-policy stance will clearly be on display. You may recall that Sestak was one of the 54 congressmen to sign the J Street–inspired Gaza letter. J Street supported Sestak and cooed about his foreign-policy stances:

He brings this philosophy into his work on American foreign policy and has insisted that at the time of the invasion of Iraq, the United States “should have simultaneously pursued a regional diplomatic offensive against what is the real clear and present danger in the region: the Israeli-Palestinian conflict and the lack of democratic institutions in the region.” … Crucially, Congressman Sestak believes that the United States needs to pursue a “diplomatic surge” with Iran. He argues that Iran is strongly disinterested in having a chaotic Iraq located next-door and that as such, an American withdrawal can be used to create diplomatic leverage with Iran.

How’s that diplomatic surge working out? If Sestak slays Specter, many Republicans will cheer that the man who gives opportunism a bad name will finally gave gotten his due. However, for supporters of Israel, there could hardly be a worse addition to the U.S. Senate than the congressman from J Street.