As Mitt Romney appeared be heading toward victory in the GOP Florida primary Tuesday, the former Massachusetts governor defiantly defended the intensely negative campaign he ran in the state.

Following his embarrassing loss in South Carolina to Newt Gingrich, Romney said he learned that he can’t sit back and “let charges go unanswered.”

“We were vastly outspent with negative ads attacking me,” Romney told reporters outside of his Tampa headquarters. “And we stood back and spoke about President Obama, and we suffered the consequences of that.

“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 have served me well here.”

Since losing South Carolina to Newt Gingrich in a landslide, Romney has been relentless in his attacks on his main rival, both in his public comments and through the barrage of negative televisions ads consuming the airways. At a certain point, political experts started to wonder whether it was overkill, as Gingrich started dropping in the polls.

It has been estimated that the Romney campaign and “Restore Our Future,” the super PAC supporting him, have spent $15 million on ads—more than 90 percent of them negative. By contrast, Gingrich and his supporting super PAC have spent about $4 million.

The state is considered a key primary battleground because of its 50 delegates and because the diversity of the population makes it a good testing ground for the general election. “Doing well in Florida is a pretty good indication of your prospects nationally,” Romney noted.

A Florida Republican Party spokesman estimated that about 2 million Floridians will cast ballots in this primary—and roughly 600,000 have already done so through early voting or absentee ballots.

Romney said he “would like to spend more of our time focusing on President Obama. 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. “

Gingrich’s attacks, he added, “have really been quite sad and painfully revealing about the speaker and what he’ll say and do to take the nomination. I just can’t stand back and let him say those things about me without responding.”

Independents and swing voters ultimately decide presidential elections, and they have been known to have little tolerance for negative campaigns. Asked whether the negativity being displayed in Florida could hurt him with independents in the general election, Romney said: “It would be wonderful if campaigns were all nothing but positive, but that’s certainly not the reality.”

Recent polls indicate the strategy may be effective here: Romney could beat Gingrich in Florida by double-digit percentages.  But 75 miles away in Orlando, Gingrich wasn’t conceding anything.

“This is a long, long way from being over," Gingrich told reporters. He said that the race wouldn’t be decided until June or July, “unless Romney drops out earlier.”