JACKSONVILLE, Fla. (AP) - An aggressive Mitt Romney repeatedly
challenged Republican presidential rival Newt Gingrich in a
fast-paced campaign debate Thursday night, ridiculing the former
House speaker's call to build costly projects in key primary states
and to colonize the moon.

Romney vehemently denied Gingrich's own accusation that he
anti-immigrant - more so than any other candidate. And, as charges
flew back and forth, Gingrich rebutted any suggestion that he
couldn't rein in surging federal spending.

"You don't just have to be cheap everywhere. You can actually
have priorities to get things done," Gingrich declared, saying
that as speaker of the House he had helped balance the budget while
doubling spending on the National Institutes of health.

The debate was the second in four days in the run-up to next
Tuesday's Florida primary. Opinion polls make the race a close one
- slight advantage Romney - with two other contenders, former Sen.
Rick Santorum of Pennsylvania and Texas Rep. Ron Paul far behind.

Gingrich's upset victory in the South Carolina primary last week
upended the race for the nomination to oppose Democratic President
Barack Obama in the fall, and Romney in particular can ill-afford a
defeat on Tuesday.

While the clashes between Gingrich and Romney dominated the
debate, Santorum drew applause from the audience when he called on the two front-runners to stop attacking one another and "focus on
the issues."

"Can we set aside that Newt was a member of Congress ... and
that Mitt Romney is a wealthy guy?" he said in a tone of
exasperation.

There were some moments of levity, including when Paul, 76, was
asked whether he would be willing to release his medical records.
He said he was, then challenged the other three men on the debate
stage to a 25-mile bike race.

He got no takers.