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ABC News' Michael Falcone reports:

TAMPA, Fla. - If Mitt Romney prevails over Newt Gingrich in Florida, as he is expected to do, it will be in no small part because he's been preparing for victory here since last June.

Or, more accurately, since 2008.

The Romney campaign has been building its operation in the state for months and aides see the primary as the culmination of an aggressive effort to get a jump on the competition, particularly by reaching out to the thousands of Floridians who vote early or by absentee ballot.

More than half-a-million Republicans requested absentee ballots this year and more than 338,000 returned them as of Monday, according to Florida election officials. Another 293,000 voted early, bringing the total number of GOP votes cast even before polls opened Tuesday morning to more than 632,000.

And if you were one of those early or absentee voters, here's what you might have received from the Romney campaign: first, a brochure in your mailbox urging you to vote for the former Massachusetts governor; next, one or two personal phone calls with the same message. And if you were still holding on to an absentee ballot close to Election Day, you likely got a knock on the door by a Romney campaign volunteer.

Romney's senior Florida strategist, Brett Doster, said that members of the Florida staff were focused on "getting voters in the bank before Iowa and New Hampshire had even taken place."

Early voting started 10 days ago and the first absentee ballots were mailed beginning in late December.

Romney's team had a head start. They used voter lists collected four years ago when their candidate came in second in the state to the eventual Republican nominee, Sen. John McCain. They also re-activated supporters who were with Romney four years ago and recruited new ones.

Doster worked alongside the campaign's state director, Molly Donlin, a veteran of Rudy Giuliani's 2008 campaign in Florida, Alberto Martinez, a Florida political operative who worked on Marco Rubio's U.S. Senate campaign in 2010, and five paid staff members dedicated to the Sunshine State.

"There was a very intelligent decision this time around to do more with less," Doster said in an interview with ABC News at the Romney campaign's Tampa campaign headquarters.

From their war room overlooking the sparkling waters of the Tampa Bay, they organized an effort that included tens of thousands of door knocks and thousands of phone calls through technology that allows volunteers to call potential supporters from their own homes.

Donlin, who started her job with the Romney campaign here on June 1, said the sheer size of the state and the diversity of its electorate presented a specific set of challenges. She saw Florida "as five states in one."

And the campaign's "more with less" strategy was heavily reliant on an aggressive television advertising strategy to reach voters from Miami to Pensacola.

The first campaign ads hit television stations in Florida starting on Jan. 3, the day of the Iowa Caucuses, and more than a month before Tuesday's primary. Since then, Romney's team put up four more commercials, including a Spanish-language spot. Two of the ads unveiled after the South Carolina primary specifically attacked Romney's main rival, Newt Gingrich.

Romney and his super PAC allies more than quadrupled the amount that Gingrich and his super PAC supporters spent on the Florida airwaves.

"The number one light switch that gets turned on within the last few weeks is people's level of attention," Doster said.

On Tuesday morning, four hours after polls opened in Florida, Romney paid a visit to his Tampa headquarters where he found about three-dozen volunteers making get-out-the-vote calls. Some of the office windows look out onto the Tampa Convention Center, one of the buildings that will host this summer's Republican National Convention, where Romney hopes to be officially nominated as the party's presidential candidate.

Romney picked up the phone to make a few calls, himself.

"Have you been out to vote yet?" he asked one potential voter. "I hope you get a chance to get out and vote because this is an important election. We've got to decide who it is that is best to take on Barack Obama, and I believe I'm the right person."