PHILADELPHIA, Oct. 4 (UPI) -- Rocker Bruce Springsteen performed a brief solo set in Philadelphia Saturday to promote Democrat Barack Obama's presidential campaign.
Springsteen played to an audience estimated at 50,000 at a "Vote for Change" rally two days before Pennsylvania's voter registration deadline, KYW-TV Philadelphia, reported.
Pennsylvania Gov. Ed Rendell -- a former mayor of Philadelphia -- told the crowd the campaign is "going to get mean" as it enters its final four weeks.
"It's going to get tough and it's going to get dirty," Rendell said.
Officials with Republican John McCain's campaign have promised an aggressive effort between now and Election Day to try to sow doubt in voters' minds about Obama's fitness to be president.
Springsteen is scheduled to perform with Billy Joel Oct. 16 in New York at a fundraiser for Obama. His appearance in Philadelphia Saturday was part of a road trip that will take him to Ohio and Michigan as well, the Hartford Courant reported.
Citing the Springsteen fan site Backstreets.com, the newspaper said Springsteen is to perform Sunday at Ohio State University and Monday at Eastern Michigan University.