"Now, I am under no illusions that suddenly I'm going to have a rubber-stamp Senate. I've got Democrats who don't agree with me on everything, and that's how it should be," Obama said.
Meanwhile, political observers will be dissecting the president's news conference to determine whether he will put his favorable ratings and political capital on the line or keep most of his legislative battling ahead behind closed doors.
Leadership aides on Capitol Hill anticipate that perhaps the biggest White House push will come on a health care plan that includes a public option, a component that is of great concern to the insurance industry that Obama hopes to keep at the negotiating table throughout the legislative process in order to avoid a 1994-style blowup.
One new role Obama is expected to play as he heads into his next 100 Days is that of fundraiser-in-chief. The president has already headlined two fundraisers for the Democratic National Committee where he helped collect nearly $3 million.
He also e-mailed supporters about his endorsement of Scott Murphy, the new Democratic congressman from upstate New York. Other than that toe-dipping, Obama has shied away from pure politics.
But Specter's party switching, 100th day gift to Obama kicked off what is expected to be a more overtly political phase of his presidency as he helps to bolster Democratic bank accounts in advance of next year's midterm elections.
After attempting to clear the Pennsylvania Democratic primary field with his and Biden's endorsement of Specter this morning, Obama is also scheduled to shake the money tree for Senate Majority Leader Harry Reid, D-Nev., next month in Las Vegas.
The two Democratic campaign committees on Capitol Hill have announced the president will be headlining a June 18 fundraiser in Washington, D.C., to help fill their midterm coffers.
As he takes on that more partisan task, the president will strive to strike the balance of party leader without tarnishing his strong support from the key ideologically centrist Americans.