## Politics

I don’t believe in any Eleventh Commandment. I think the Democratic Party apparatus has every right to intervene in a primary battle when they expect to gain some strategic advantage from doing so. Sometimes (not always), cutting off a primary challenge at the pass is in the best interest of a party. Sometimes (not always) one of the candidates can do more to support the legislative agenda. Sometimes (not always) one of the candidates has a clear electability advantage. If you want to intervene under these circumstances, intervene away.

But it’s hard to see what OFA and the White House are getting by intervening on behalf of Arlen Specter.

Look, I get it: Arlen Specter did the White House a huge favor. He switched parties, costing the Republicans about a dozen news cycles and possibly their ability to defeat health care. Earlier in Obama’s term, while still a Republican, Specter had supported the stimulus package. And he’s been a very reliable liberal vote since last summer (perhaps not coincidentally, when Sestak announced his challenge). You don’t want to discourage anyone from moving in your direction; I was skeptical of Sestak’s challenge for that reason. I’m also skeptical that, over the long-run, Sestak’s going to wind up being any more liberal than the current reboot of Arlen Specter.

But the primary challenge has happened. In fact, it’s coming to fruition next week. The cat’s out of the bag. And we shouldn’t forget the one clear advantage of a primary challenge: it provides a candidate with a dress rehearsal for November, and gives a party some option value in picking its candidate.

So far, Joe Sestak has made the most of that dress rehearsal. He’s pulled into a near tie with presumed GOP nominee Pat Toomey in both Quinnipiac and Rasmussen polling, whereas Specter trails in the same polls by 7 and 12 points, respectively.

There’s a good mechanism to explain the change: Sestak wasn’t very well known before, but now he’s becoming more so. We have to be a bit careful, though, because there’s sometimes a bounce surrounding a primary battle than can later dissipate. (See also: Deeds, Creigh).

But if there’s a bounce, why hasn’t Specter received one? Instead, in the Quinnipiac poll, Specter’s favorability ratings have dropped eight points among the November electorate.

Specter is not going to win very many votes among Republicans, the party which he deserted last year. Independents view him negatively: 30-58, in the Quinnipiac poll. The only way he’s going to win (and it’s a necessary rather than sufficient condition) is with monstrous, enthusiastic Democratic support.

So if that support is there, let’s see it. Let’s see him beat Joe Sestak, who is not an overwhelmingly brilliant candidate. Let’s see if he can clear that hurdle. Democrats have benefited from his flip-flops — in a clear and tangible way. If they’re not going to get his back, then who do you think will?

And let him do it on his own. Let Pennsylvania decide. You’ve done enough to pay back the favor.

Nate Silver is the founder and editor in chief of FiveThirtyEight.

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### The Republican Establishment Is Waiting On The SidelinesSep 3, 2015

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