President Barack Obama lends support to Pennsylvania's Democratic candidate for U.S. Senate, Joe Sestak, on Monday during a fundraiser in Philadelphia.

ENOLA — Pennsylvania's Democratic candidate for U.S. Senate, Joe Sestak, got some badly needed fundraising help in his closely contested race from President Barack Obama, who had backed Sestak's opponent in a divisive and hard-fought primary.

Before a crowd of several hundred supporters at the Pennsylvania Convention Center in Philadelphia, the president cast Sestak as a Washington outsider who will be outspent by Republican candidate Pat Toomey and "special interests" that helped cause the recession.

"Everybody has been talking about insiders in Washington," Obama said, according to a White House transcript. "Well, Joe is not one of the insiders who's been part of the problem. Instead, he's been solving problems in Washington. He didn't go there with a liberal agenda or a conservative agenda."

The evening rally and dinner was Obama's first appearance with Sestak since Sestak became the Democratic nominee. Sestak, a second-term House member from a Philadelphia suburb and a former Navy vice admiral, won the party nomination in May in a come-from-behind victory over Republican-turned-Democrat Arlen Specter.

Specter, a five-term incumbent, was supported by Obama, Pennsylvania Gov. Ed Rendell and the Democratic Party — and Sestak is using that victory over the White House and the party to his advantage in an election year when voters are being tough on incumbents. One of his recent TV ads flashes a newspaper headline that says, "Nonstop Joe Sestak refuses to join 'the establishment."'

Already, millions of dollars in television ads are flowing into the race from outside the state, a sign that national party committees and interest groups have made Pennsylvania a priority. The Senate race could forecast which political party will win the swing state in the 2012 presidential election.

Sestak and Toomey are ideological opposites, with lifetime voting records on either end of the spectrum: Sestak liberal, Toomey conservative.

Toomey, a former congressman and businessman, opposes the major points of Obama's agenda.