ABOARD THE ROMNEY PLANE EN ROUTE IOWA—Mitt Romney's campaign is mocking President Barack Obama's decision to release a campaign ad focused on the Republican candidate's repeated suggestion that Big Bird shouldn't receive public funding.

Kevin Madden, a senior Romney adviser, told reporters on board the candidate's plane Tuesday the campaign isn't taking the Obama's latest offensive seriously.

"Right now, you've got 23 million Americans struggling to find work. You've got household incomes going down. You've got a federal deficit, federal debt that's over 16 trillion dollars," Madden said. "I find it troubling that the president's message, the president's focus 28 days out from Election Day is Big Bird."

On Tuesday, the Obama campaign released an ad trashing Romney for his suggestion at last week's debate that he would cut funding for "Sesame Street" as part of an overall effort to cut the federal deficit. It's a line that Romney has been saying on the trail for more than a year, but Democrats immediately seized on the Big Bird comment at the debate as proof Romney is ill-equipped to be president.

Privately, Romney aides acknowledge they understand why the Obama campaign is playing up the Big Bird line. The campaign's internal numbers showed the line didn't play well with voters, according to one aide, and Romney notably hasn't repeated it since.

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Speaking to reporters on the plane, Madden said Romney would continue to focus "acutely on jobs and the economy and what he can do to create a more prosperous future for the American public."

"That is a much bigger focus," Madden said. "We are focused on the big issues that the American people are focused on."

Asked about the latest Pew poll which suggested Romney has new momentum after last week's debate, Madden said the governor and his aides are not letting the positive numbers go to their heads.

"Look, this is a campaign that's never gotten too high when things are good and too low when things are bad. I think we remain--the governor, in particular, remains--very focused at the task at hand," Madden said. "You can't put too much stock in this idea of momentum. I think it's a very elusive thing. We still believe that this is going to be a campaign that is very close."