Franklin & Marshall College political analyst Terry Madonna said that Obama appeared with Specter in Philadelphia and earlier in the day in Pittsburgh to give him some Democratic bona fides.
"The debate in the primary is all about whether Specter's conversion is real, whether he's a real Democrat," Madonna said. "This is about making it clear he's a loyal Obama Democrat, and giving him the approval and imprimatur of the president."
It was also about raising money.
Supporters paid $2,400 to attend an afternoon reception and hear Obama speak. A dinner afterward was for those who paid either $10,000 or raised $50,000.
Specter campaign manager Christopher Nicholas said that supporters were "within striking distance" of their fundraising goal of $2.5 million for the events, to be split between the Specter campaign and the Democratic Senate Campaign Committee.
Chris Doherty, the Democratic mayor of Scranton, was among those at the reception. He said that Specter's record of working with Democratic elected officials in the state made it easier for him to gain acceptance in the party.
"Five years ago we had a flood in Scranton and 450 houses were wiped out," Doherty said. "We called him, and got the Army Corps of Engineers working on the problem. I've been mayor eight years, and he's come to see us every year."
J. Whyatt Mondesire, Philadelphia Sunday Sun publisher and local NAACP president, said that he had nothing against Sestak, but was supporting Specter.
"He's a nice guy," Mondesire said of Sestak. "But look at all the Democrats here [for Specter]. You have so many leading Democrats, and a lot of the clergy."
Sestak's campaign released a statement yesterday criticizing Specter for leaving Washington to campaign, but Sestak spokesman Jonathan Dworkin said that Sestak himself was with his family and wouldn't comment on the event.
Sestak's father, retired Navy Capt. Joseph A. Sestak, died Sunday.
Obama spent much of his speech at the reception talking about health-care reform.
He said that Specter knew about the issue firsthand, having survived cancer, "because he was able to receive some of the best health care available in the world, and also because he's a tough son of a gun."
At the dinner, Specter said of Obama, "It's great to have him as a president, it's great to have him as a friend - and it's perhaps greatest to have him as a fundraiser."