Romney challenges Santorum’s debate answers

>>> less than a week before two critical republican primary contests, last night's debate the 20th and final debate quickly turned into a romney -santorum smackdown, each of them giving as good as they got. nbc's petr peter alexander reports from michigan.

>> reporter: mitt rom no wasted no time today trying to capitalize on sabtor up's debate.

>> i don't think i've ever seen a politician --

>> reporter: he made a mistake by backing president bush 's overhaul.

>> it was against the principles i believed in, but, when you're part of the team, sometimes you take one for the team for the leader and i made a mistake. politics is a team sport , folks.

>> reporter: romney took a swing at that comment, too.

>> he talked about this as taking one for the team. i wonder which team he was taking it for?

>> reporter: riding a wave of momentum.

>> i'm here to talk about a positive solution to the problems that confront this country.

>> reporter: santorum who insists he's the true conservative in the race mocked romney 's assertion that he balanced budgets as the governor.

>> michael dukakis balanced the budget does that make him qualified to be president of the united states ? i don't think so.

>> reporter: romney fired back.

>> while i was fighting to save the olympics, you were fighting to save the bridge to nowhere .

>> reporter: as romney prepares to give a major economic speech tomorrow at ford field , home of the detroit lions , his supporters will begin airing this ad, re-telling the dramatic accounts of romney 's efforts years ago that helped safely bring home a former business partner 's missing daughter.

>> what a lot of people say are nearly impossible, but for me the most important thing he's ever done is to help save my daughter.

>> reporter: one more thing about that ad, it's nearly ident cal to the romney ad they aired four years ago. they tell nbc news that it purchased the footage from romney 's old mead why team and while that follows the letter of the law it blurs that line between campaigns and super paks.

>> peter alexander on the campaign trail.