ABC News' Michael Falcone reports:

CLINTON, Iowa - Call it the Mitt Romney version of compassionate conservatism. He's a fan of public broadcasting, and he's got nothing against Big Bird, but his love for PBS and the iconic "Sesame Street" character only goes so far.

In response to a voter's question about how he would reduce spending and rein in the national deficit if elected, Romney said that some programs would have to go.

"You might say, 'I like the National Endowment for the Arts.' I do. I like PBS. We subsidize PBS. Look, I'm going to stop that. I'm going to say, 'PBS is going to have to have advertisements,'" Romney told a crowd at a deli in this Eastern Iowa town. "We're not going to kill Big Bird, but Big Bird's going to have to have advertisements, all right? And we're going to have endowments for the arts and humanities but they're going to be paid for by private charity not by taxpayers - or by borrowers."

It was not the first time Romney has proposed either cutting or finding new sources of revenue for certain government programs, including PBS, but on Wednesday he laid out his criteria for how he would determine which to slash.

"My test is - is a program so critical that it's worth borrowing money from China to pay for it?" Romney said.

One of his solutions "is to stop certain programs - stop them, close them, turn them off - even some you like."

On a day when a new CNN-Time poll showed Romney climbing into the lead in the state where voters will gather for the caucuses in just six days, Romney cast the nation's spending problem in moral terms.

"I happen to think it's immoral for us to keep spending money we don't have and passing on to our kids our obligations," the former Massachusetts governor said. "We just can't go on like this."