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 mini dress.
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.
24.com publishes all comments posted on articles provided that they adhere to our Comments Policy. Should you wish to report a comment for editorial review, please do so by clicking the 'Report Comment' button to the right of each comment.
Shakira used her star power to share the burden and prioritize the protection of refugees. Read More »
The Hollywood Wives novelist and actress Jackie Collins has died of breast cancer at age 77. Read More »
Your Spring guide.
SandtonDante Personnel RecruitmentR12 000 - R18 000 Per Month
SandtonNeo Batho (Pty) LtdR16 000 - R20 000 Per Month
RandburgNeo Batho (Pty) LtdR25 000 - R30 000 Per Month
HousesR 1 900 000
TownhousesR 1 365 000
Commercial PropertyR 43 500 000