STARTING TO LOOK A BIT LIKE CONNECTICUT ’06…. Whether he deserves it or not, Sen. Arlen Specter will, like all Democratic incumbents, enjoy the support of the party establishment, including the White House. Rep. Joe Sestak (D-Pa.), who’s all but certain to challenge Specter in a Democratic primary, told Greg Sargent this afternoon that even a call from the president wouldn’t discourage him.

Asked what he would do if Obama himself made the request, Sestak reiterated his respect for the President but said it wouldn’t make a difference. “At the end of the day my responsibility is to [the people] here in Pennsylvania,” he said.

Obama has said he’ll back Specter to the hilt for re-election, but Sestak said even a Presidential endorsement isn’t insurmountable for him. “As important as the President’s endorsement is, and who wouldn’t want President Obama’s endorsement, at the end of the day I don’t believe that most voters vote because someone else endorsed someone,” Sestak said.

I not only think that’s true, I also think Sestak understands very well how this game is played. Obama will support the Democratic incumbent, and then support the Democratic nominee. If Sestak wins the primary, he’ll have Obama’s support.

We saw a similar dynamic in Connecticut in 2006*. Joe Lieberman was the Democratic incumbent, and party leaders (including Obama) rallied to support his campaign. When he lost the primary, those same party leaders threw their support (with varying degrees of enthusiasm) to Ned Lamont.

So, from Sestak’s perspective, why not run? It may look like he’s bucking the party’s leadership, but that’ll be the same leadership that embraces him with both arms should he win the primary.

* Post Script: The difference between Pennsylvania and Connecticut, in case there’s any lingering confusion, is that Specter wouldn’t be able to run as an independent after the primary. He who loses the primary will have to wait until the next election cycle.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.