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.
American Pie actor, Jason Biggs, found himself in hot water after tweeting a joke shortly after the crash of Malaysian Airline flight MH17. Read More »
The reclusive author of To Kill a Mockingbird, Harper Lee, has said she didn't authorise a new memoir about her life. Read More »
Another season soon!
It's all good!
We want more!
Cosy with PHfat!
Has a new hobby!
4 must watch shows!
The queen is a fan!
Goes into space!
National Savings Month is not only this month, it is every month from your very first salary slip, an expert warns OneRandMan and all South Africans.
RandburgFig Technology (Pty) LtdR10 000 - R15 000 Per Month
Port ElizabethFocus Personnel Trust
PretoriaPeople Source (Pty) Ltd
HousesR 5 500 000
HousesR 3 300 000
HousesR 19 500 000