MILWAUKEE—No one is immune from an April Fools' Day prank—not even Mitt Romney.

Ahead of a meet and greet with voters at a restaurant here, Romney's staff decided to play a practical joke on their boss. They set up an event room identical to the room where the candidate was to meet with voters over pancakes this afternoon, right down to the red, white and blue Romney signage, American flags and black draping.

But it lacked one vital thing: actual voters.

Rep. Paul Ryan and Sen. Ron Johnson—two key Romney surrogates here in Wisconsin—were in on the joke. Ryan introduced the candidate as planned in the empty room, as Romney and Johnson listened off stage. But as Romney prepared to enter the room to his usual soundtrack of Kid Rock's "Born Free," his staff warned him that turnout at the event had been lighter than expected.

"I go in there, and it's completely empty. There's nobody there!" Romney giggled, as he later recounted the prank to his audience at the real event. "I thought, oh boy, this is going to look really bad on the evening news, let me tell ya."

The worst part, Romney explained: The prank was caught on camera.

"They turned me into the April Fool this morning!" Romney laughed, admitting he had forgotten about the holiday. "This is known as forgive, but remember. I tell ya, we're going to remember this."

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