While campaigning for Mitt Romney, John McCain took a swipe at fellow Republican Newt Gingrich with a space related joke.

Romney is a former governor for Massachusetts and a candidate for 2012 presidential nomination by his party.

"I think we ought to send Newt Gingrich to the moon and Mitt Romney to the White House," Politico quoted McCain as saying.

The senator and '08 candidate also told the crowd in Florida that it's a two-man race now, and suggested Romney could pick Marco Rubio as his vice-presidential running mate, CBS news reported.

"I think it's very likely that it's a two-person race... I think it's pretty clear that Ron Paul has reached a ceiling as he did in 2008," he said.

"In the case of Rick Santorum, he was defeated in his own state by some 18 points in his bid for re-election. That's not the kind of credentials that people need, I think, for a winning candidate," he added.

He was also asked by an attendee to predict Romney's choice of a vice presidential running mate.

"A little straight talk? Marco Rubio," he said. (ANI)