Romney and McCain are neck-and-neck on the even of the Florida primary.

SANFORD, Florida (CNN) – For a moment Monday, Mitt Romney seemed to nominate himself for a job he doesn't want.

“It’s not really something he understands that well. He’s said it a number of times and indicated that he’d have to choose a vice president who really understood the economy. Well, I do understand the economy.” Catching himself, he added, “I’m not going to be any vice president to John McCain either, that’s not going to happen.”

With Romney and McCain locked in a dead heat in the polls on the eve of Florida primary, barbs have been lobbed back and forth all day long between the two camps.

Romney kicked it off before the sun even came up at a press conference at a gas station, criticizing McCain for the McCain-Lieberman bill that Romney says would make gas prices go up $0.50 and cost Florida families around $1,000 per year.

He added that in addition to the bill, McCain is best known for two other pieces of legislation, emphasizing that he wrote them with Democrats – McCain-Kennedy, which Romney says gives amnesty to illegal immigrants, and McCain-Feingold, which he says restricts First Amendment rights.

“If you want that kind of liberal democratic course as president then you can vote for him. But those three pieces of legislation, those aren't conservative, those aren't Republican,” Romney told a crowd in West Palm Beach.

McCain responded quickly, arguing that Romney had been a supporter of the three issues the bills target, “One thing I think we should really give Governor Romney credit for - he is consistent. He has consistently taken both sides on any major issue, he has consistently flip-flopped.”

In a statement, McCain added, “At a time of grave national security challenges abroad and real economic uncertainty at home, now is not the time for leaders whose consistency is in question.”

Tuesday night’s results will reveal whether the candidates’ efforts to drag the other into debate over their strong suits – McCain on Iraq and national security, Romney on the economy – will pay off.

– CNN Political Producer Alexander Marquardt