In his own words

The most effective TV attack ad is the kind that essentially shows the targeted candidate using his own words to attack himself.

It is anyone's guess whether underdog Democrat Joe Sestak can wrest the Pennsylvania Senate nomination away from incumbent/survivor/chameleon Arlen Specter in the primary election 12 days from now. But if Sestak does manage to stage a major upset, we're likely to look back and say that his new TV ambush on Specter was the move that changed the game - precisely because ex-Republican Specter is right there on camera, talking about how he switched parties a year ago in order to preserve his political career.

The Sestak ad is clearly aimed at the reportedly large number of Democrats who have yet to decide on a candidate. One senses that these undecideds may well be leaning toward Sestak, if only because Specter is universally known in Pennsylvania, and one can reasonably speculate that if the undecideds wanted to back Specter, they'd be in his camp already. This new ad is crafted to give the undecideds one last reason to dump Specter - and erase the senator's poll lead. Specter recently topped Sestak among Democratic voters by double digits, but his margin has since been whittled to as few as five percentage points - a situation that has unnerved Democratic leaders, notably state chairman T. J. Rooney, who told the Politico website this week that a Sestak victory would be "cataclysmic" for the party's prospects of beating Republican Pat Toomey in November.

Anyway, the Sestak ad features footage of Specter sharing a podium with his former Republican compradre, Rick Santorum, and with an effusive George W. Bush. (Bush on Specter: "I can count on this man. See, that's important. He's a firm ally.") And it closes with a freeze shot of Specter on the stump with Sarah Palin. Naturally, all that footage is designed to induce the proper Pavlovian response among Pennsylvania Democratic voters, and remind them - if they need any reminding - that Specter was not always a left-leaning lawmaker who voted for the Obama economic stimulus.

But the potential zapper is when Specter talks about his own party switch: "My change in party will enable me to be re-elected."

Sestak's media team liked that clip so much, they used it twice within a span of 16 seconds - understandably so, because it's probably their best weapon at the finish line. Democratic voters are potentially just as fed up with the political establishment as their GOP counterparts seem to be, and here is Specter, in his own words, describing himself as an establishment fixture motivated only by self-preservation.

When Specter announced his party switch 13 months ago, he also specifically spelled out his reasons for leaving the GOP this way: "I have traveled the state and surveyed the sentiments of the Republican Party in Pennsylvania and public opinion polls, observed other public opinion polls and have found that the prospects for winning a Republican primary are bleak." In terms of message, the clip in the ad is essentially the same - with the requisite soundbite concision.

A politician never looks good when he's quoted undercutting himself. Just ask John Kerry, who suffered politically in 2004 for saying, "I actually did vote for the $87 billion before I voted against it." The nimble-footed Republicans sped the footage into a Bush campaign ad, and, fairly or not, Kerry's nascent image as a flip-flopper was sealed by his own words. The risk for Arlen Specter right now is that his own words might seal the suspicion, among many undecided Democrats, that he's only driven by opportunism.

The irony is that when Specter spoke those words, he was being candid about himself. Rarely has a politician been so open and honest about being so conviction-free, and now we'll see whether Sestak can make him pay a fatal political price.