Facing a primary challenge, Specter, a longtime Republican, switched political parties in April, giving Democrats a valuable 60-vote majority in the Senate. The White House immediately said it would help Specter defend his seat, starting with a fundraiser Tuesday that was expected to raise $2.5 million.
"Arlen's not someone who came to Washington to fight for a particular ideology. He came to fight for the working men and women of Pennsylvania," Obama said. "He has a long and successful record of doing just that."
By attaching itself so wholeheartedly to Specter, the White House has tied its political fortunes to the former prosecutor. If Specter loses a strong primary challenge from Pennsylvania Rep. Joe Sestak, aides acknowledge that the Obama brand may be damaged heading into the president's own re-election in 2012.
"Candidate Obama was a transformational candidate and now he's moving forward to be a transformational president. It's a very real change," Specter said. "He's going to be successful with my help and the help of others."
For his part, the 79-year-old Specter is counting on union, White House and Democratic establishment support to hold on to his seat for another six-year-term.
Specter said he was optimistic about his chances but hardly confident, pointing to Sen. Joe Lieberman, who lost a Democratic primary and had to run as an independent to retain his seat in Connecticut. He also cited Rep. Joe Wilson, the South Carolina Republican who heckled the president last week on the floor of the House.
"If this guy from South Carolina can be a hero, what's happening in America?" Specter said at the second of two fundraising events with the president.
Earlier Tuesday, Specter spoke to the nation's largest labor organization, the AFL-CIO, and boldly predicted a pro-labor bill would pass Congress this year. He also said he would support that legislation - a reversal from when he was a Republican.
His critics were quick to note the change.
"Sen. Specter has once again changed his perspective on the union card check legislation," said Rick Santorum, a Republican former U.S. senator from Pennsylvania who lost his seat in a Democratic wave in 2006.
"I guess it's the price you have to pay the piper to get President Obama to come in and do some campaign stops for you. ... He has done a hard left turn to try to get into the good graces of this president, and obviously he is getting rewarded for that."
Santorum said Democrats would see the move for what it was: "pandering flipflops."
The White House, however, is not going to back away from Specter. Obama said Specter has worked to repair a struggling economy, increase the minimum wage and protect the Keystone State from massive state government layoffs by supporting the $787 billion stimulus package.
Painting him as above politics, Obama said Specter was a "tough son of a gun" not afraid to put his own beliefs ahead of those of party leaders - Republican or Democratic.
"You know he's going to fight for you regardless of what the politics are," Obama said.
"He and I, even when we were on the opposite side of the aisle, understood that the American people aren't looking for slogans, they're not looking for ideology, they're not looking for bickering."