TAMPA, Fla. — Mitt Romney embraced a killer instinct and leveraged a dominant political machine to crush chief rival Newt Gingrich in Florida’s Republican presidential primary.

It was a remarkable turnaround for a candidate who lost big just 10 days earlier in South Carolina.

“I stand ready to lead this party and our nation,” a jubilant Romney told cheering supporters Tuesday night in Florida, claiming a resounding victory in a state that rejected his White House bid in 2008.

Romney was beaten down as he came into Florida after Gingrich trounced him in South Carolina. The former House speaker’s triumph fueled a wave of momentum that threatened to unite anti-Romney conservatives in Florida and beyond.

Recognizing the threat, Romney had hatched a new strategy even before the South Carolina loss was official.

It would be the end of nice-guy Romney, the man who had usually saved his sharpest barbs for President Barack Obama and let his allies run the attack ads. From the start of the Florida campaign, voters here witnessed Romney’s new go-for-the-jugular approach on their television sets, debate stages, and even at Gingrich’s campaign stops.

“If you’re attacked, I’m not going to just sit back,” Romney said Tuesday, warning his competitors that the tough guy is here to stay. “I’m going to fight back and fight back hard.”

It wasn’t just Romney’s attack mode — and efforts to undercut Gingrich’s character — that guided him to victory.

He also was sitting on a ton of cash and had built an extensive statewide campaign, giving him enormous advantages in a massive state with 10 media markets where campaigns often are won on the air.

Romney and his allies ultimately poured roughly $16 million into Florida television advertising. Restore Our Future, the “super” political action committee supporting Romney, began running Florida ads in mid-December. The candidate and the super PAC also launched an aggressive campaign to court absentee and early voters.

Gingrich was overmatched in Florida on all those fronts. He and his allies turned their attention to the state several weeks after Romney’s team had begun its work. He hired local staffers just a month before the election. And he never had the money to compete. Gingrich and his allies spent a quarter of Romney’s total — roughly $4 million — on Florida advertising.

Gingrich’s fiery demeanor and Ronald Reagan comparisons turned out to be no match for Romney’s behemoth organization and newfound aggression.

The former congressman from Georgia arrived in Florida on Jan. 22 with a head of steam after his South Carolina win.

One day later, he was confident as he took the stage for the first of two debates before Florida’s primary.

But so was Romney, who had hired a new debate coach that week.

The first sign of Romney’s new strategy came early as he tore into his opponent, a former college professor who had built his candidacy on the strength of his debate performances. Among other things, Romney attacked Gingrich’s work for the mortgage giant Freddie Mac, which would soon become a Romney refrain.

“Freddie Mac was paying Speaker Gingrich $1.6 million at the same time Freddie Mac was costing the people of Florida millions upon millions of dollars,” Romney said.

Despite that subpar debate performance, Gingrich initially drew thousands of hopeful Republicans to airport hangars and hotel ballrooms across the state. Fearing crowds might threaten public safety, a fire marshal blocked hundreds from entering a packed venue on the Space Coast last week. And for a time, Gingrich clearly believed he would prove that South Carolina wasn’t a fluke.

“I predict people power will beat money power,” an almost giddy Gingrich told thousands of cheering supporters in Sarasota last week. “If we win the primary next Tuesday I believe I will become the Republican nominee. So, as the nominee, I get to come back to Tampa in August. We’ll have a really big rally for that.”

The giddiness didn’t last long.

That same day, Romney began running a blistering new ad on Florida television stations across the state. It was a first for a Romney campaign that had been content, up to that point, to leave the negative advertising to outside allies. No more.

“While Florida families lost everything in the housing crisis, Newt Gingrich cashed in,” the narrator said. “Gingrich resigned from Congress in disgrace. And then cashed in as a D.C. insider.”

Gingrich had previously shrugged off questions about his consulting work for Freddie Mac. But Romney wouldn’t let Gingrich off the hook in Florida. Two days after the ad began running, Gingrich suffered perhaps his greatest setback on an unlikely stage.

The candidates met Thursday night in Jacksonville for the final debate before the primary.

Romney supporters packed into the auditorium to help win the applause battle. And Romney researchers found a gem among Gingrich’s personal investments hours before the debate.

Gingrich walked into a trap when he criticized Romney for investing in funds that include stock from Fannie Mae and Freddie Mac.

“Mr. Speaker, I know that sounds like an enormous revelation, but have you checked your own investments?” Romney asked a stone-faced Gingrich. “You also have investments through mutual funds that also invest in Fannie Mae and Freddie Mac.”

It was like a punch to the stomach for Gingrich, who needed a strong showing to reclaim the momentum. He was speechless and wouldn’t recover that night or in the days that followed.

Florida polls had already started swinging wildly in Romney’s favor. And he didn’t take his foot off Gingrich’s neck.

At a campaign stop the next day, Romney likened Gingrich to Goldilocks, the fairy tale character who complained of the temperature of her porridge. He repeated the jab the next day. And Romney dispatched high-profile surrogates to Gingrich events, ensuring that no attacks would go unanswered in real time.

The strategy produced uncomfortable moments for Gingrich and sometimes clouded his message. Surrounded by reporters and cameras, a Gingrich spokesman forced an argument with a Romney representative, Utah Rep. Jason Chaffetz, about Fannie Mae and Freddie Mac.

It was an unusual approach for a campaign that appeared to be in a tailspin.

Gingrich’s crowds started to shrink. And the campaign further alienated voters by struggling with the logistics of campaigning in a large state — often arriving at events 90 minutes late in the campaign’s final days.

Romney didn’t let up.

The campaign aired a second attack ad four days before the primary featuring an NBC News broadcast from 1997 about Gingrich’s ethical problems as the House speaker. The Romney campaign refused to take the ad down after objections from NBC, a dispute that only heightened the ad’s exposure.

But Gingrich was defiant until the end.

On Tuesday, he predicted the race would continue for another six months regardless of the Florida results. “Unless Romney drops out earlier,” he quipped.

Romney has signaled that he won’t back off his aggressive strategy so long as Gingrich is within striking distance, saying, “I’m not going to stand back and allow another candidate to define me.”

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