Updated

President Obama headlined a fundraiser Monday evening for Democratic Congressman Joe Sestak's U.S. Senate bid in Pennsylvania, telling an enthusiastic crowd in the City of Brotherly Love, "the main reason I'm here is to stand next to your next Senator, Congressman Joe Sestak!"

But Sestak wasn't always the president's choice for the job. "Everybody knows that the Washington establishment Democratic Party didn't want me in the race," Sestak told Fox News Monday. "I bucked the party establishment because I wanted to fight for the middle class."

A few short months ago the administration actively tried to convince the Democratic congressman not to challenge Democratic Senator Arlen Specter in the Pennsylvania primary. President Clinton discussed the possibility of a White House or administration appointment with Sestak, in exchange for Sestak's withdraw as a candidate. White House Chief of Staff Rahm Emanuel acted as a liaison with former President Clinton.

Sestak trails Republican Pat Toomey in all the recent polls but finds himself within the margin of error in the most recent Critical Insights Research poll of likely voters, with nearly a quarter still undecided. Of his opponent's presidential fundraiser, Toomey told Fox, "It reminds Pennsylvania voters of the fact that Joe Sestak has been in lockstep with Barack Obama."

The president is popular in Philadelphia, but not statewide. Republicans consider the Pennsylvania Senate race a must-win if they hope to pick up 10 seats in November to win back the majority. Sestak trailed Specter in the weeks leading up to his primary win in May. Obama was actively working for Specter and he lost. Democrats worry the president's visit might not have the positive impact that Sestak is counting on.