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.
A nearly flawless copy of Superman's comic-book debut has sold for a super-powered price: $3.2m. Read More »
Robin Williams, a brilliant shapeshifter who could channel his frenetic energy into delightful comic characters or harness it into richly nuanced work, has died in an apparent suicide. Read More »
Local rising star!
A quick interview!
Talks from Italy!
Her life and career!
A short sexy chat!
Our own celeb guru!
Quickie time again!
A quick chat!
GautengR40 000 - R50 000 Per Month
KwaZulu-NatalHire ResolveR450 000 - R550 000 Per Year
Western CapeHire Resolve