(Image Source: Joe Raedle/Getty Images)

TAMPA, FL - Mitt Romney divulged for the first time some of the lessons he learned during the South Carolina primary, saying that he now knows he "can't let charges go unanswered" and vowed not to "sit back" as the campaign continues to grow more and more negative by the day.

"You know in South Carolina we were vastly outspent with negative ads attacking me and we stood back and spoke about President Obama and suffered the consequence of that and also some good debates by Speaker Gingrich," said Romney, addressing the press outside his Tampa headquarters, where volunteers were calling voters to remind them to head to the polls.

Romney spoke at length about what he learned during the week leading up to the South Carolina primary, where he finished second to Gingrich. It was the first time that the candidate himself offered a glimpse into the change of strategy his campaign took between South Carolina and Florida.

"I don't know that we have all the lessons out of Florida yet because we haven't counted the votes yet, but if we're successful here it'll be pretty clear that when attacked, you have to respond," said Romney. "And you can't let charges go unanswered. And when that occurs you're going to suffer from it."

"Of course some weeks in politics are good and some are not," said Romney. "You know, it so happened that there was a recount in Iowa when I was in South Carolina and what was a win became a loss in Iowa and a couple of other things - Rick Perry dropped out and supported Speaker Gingrich, he had a couple of good confrontations with moderators at the debates. When those things happened, he got a good boost. And I needed to make sure that instead of being outgunned in terms of attacks that I responded aggressively and I think I have and hopefully that will serve me well here."

"I would like to spend more of our time focusing on President Obama," he said. "That's ultimately what's going to be essential to taking back the White House. But I'm not going to stand back and allow another candidate to define me. His comments most recently attacking me have been really quite sad and I think painfully revealing about the speaker and what he's willing to say and do to try to take the nomination. So I just can't stand back and let him say those things about me without responding."

"We came to Florida and Speaker Gingrich didn't have two good debates. I did," said Romney to cheers. "And we responded to the attacks that were coming to us, I'll tell you if you're attacked I'm not going to just sit back I'm going to fight back and fight back hard."

Romney mentioned a Suffolk University poll that found that Floridians considered Gingrich's campaign the more negative one in the state, and said that with that considered, Gingrich "can't really whine about negative campaigning."

"He launched a very negative campaign in South Carolina and when the people here in Florida looked at the different campaigns and concluded his was the most negative," said Romney.