PORT ST. LUCIE, Fla. (AP) - Republican presidential candidate Newt Gingrich says he'll stay in the race until the national convention this summer even if he loses Tuesday's Florida primary.

Gingrich says, "Why don't you ask Gov. Romney what he will do if he loses" in Florida, saying two recent national polls have Gingrich ahead.

The former House speaker's comments raise the prospect of an extended struggle inside the party.

Meanwhile, front-runner Mitt Romney is pouring on the criticism of his rival in TV ads airing across Florida. A new ad mentions how Gingrich received an ethics reprimand from the House and was ordered to pay a $300,000 fine.

The ad, which uses an NBC News broadcast, is raising objections from former network anchor Tom Brokaw, who says he doesn't want his role as a journalist "compromised for political gain by any campaign."

In person, Romney's criticism is directed at President Barack Obama, calling the president "detached from reality." He says Obama's "pretty please" foreign policy is not working terribly well, and says Obama wants to add 100,000 troops, not cut them.