Below is the relevant part. Pretty good one for such stick up their butts.
Romney explained how his staff and his two Republican backers – Ryan and Sen. Ron Johnson of Wisconsin – had pulled off the prank.
"My staff says to me, 'there's a small, it's a small, we didn't get much of a turnout this morning, it's really, it's really small but it'll be OK, it'll be OK,'" Romney recounted. "And so I hear Paul Ryan goes out there, gives the same introduction - what he just said. He's down there – 'and so now let's welcome Ron Johnson and Mitt Romney, the next president of the United States.'"
A press aide said the advance team – who cooked up the trick on Saturday night – played canned applause so the governor would not suspect the trick.
"So the two of us go out there and I go out there and it's completely empty. There's nobody there," Romney told the audience, while his smirking staffers laughed along. "It's like, oh boy, this is going to look really bad on the evening news, let me tell you."