Obama Rallies With Katy Perry, Dave Matthews, John Mellencamp

Katy Perry performs at a campaign rally for President Barack Obama at the Delta Center on November 3, 2012 in Milwaukee, Wisconsin.

Dave Matthews and Bill Clinton boosted a rally for President Obama in Virginia Saturday, which attracted an estimated 24,000 people. Clinton, who was losing his voice from campaigning, said he had given "my voice in the service of my president," the AP reported.

The former commander in chief also praised Obama's economic plan, saying he had done well after being dealt a bad hand.

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The rally comes on a day in which thousands came out to see the president at a total of four rallies, some of which included star power. Five thousand-plus people saw the president with John Mellencamp in Debuque, Iowa. More than 20,000 attended an event for president featuring Katy Perry in Milwaukee, WI, where the pop star wore a skin-tight minidress with Obama's campaign slogan "Forward" emblazoned across it.

Perry came on stage at Saturday's event initially wearing a red, white and blue dress and holding a microphone shaped like the Statue of Liberty's torch. But after her first song, a cover of Al Green's soul hit "Let's Stay Together," she tossed aside the dress to reveal the bright blue minidress.

Obama's slogan "Forward" is also Wisconsin's state motto.

Perry paused midway through her set to make a pitch for donations to victims of Superstorm Sandy. Obama's rally with Perry comes before he's set to be in Madison on Monday with rocker Bruce Springsteen.