By Brendan Farrington

A.P. writer

TALLAHASSEE, Florida—So close to Republican hearts, Florida is a state of bewilderment for the party now.

Its changing population, shifting political alliances and states-within-a-state diversity make it a wild card in the race for the Republican presidential nomination, and a card that matters. The state that gave new meaning to elections too close to call is playing its unpredictable self again.

Quite by design, Florida now finds itself in play after years of little impact in nomination contests.

And it looms as a battleground in the fall—“a 50/50 state,” as Democratic consultant David Beattie put it, one offering 10 percent of the 270 electoral votes needed for the presidency.

In the Jan. 29 Republican primary, Rudy Giuliani will rise or fall here as a national prospect. His rivals can find their stride in Florida or trip precipitously, after earlier contests gave victory to several of them but a clear shot at the prize to none.

“Florida is going to be a donnybrook, a four-way donnybrook,” predicted Charles Black. He advises Arizona Sen. John McCain, who came to Florida with a head of steam after winning the South Carolina primary Jan. 19.

Most Republican candidates will focus on the corridor between Tampa and Daytona Beach along Interstate 4, a swing part of the state that has seen much growth and is home to roughly two-thirds of the Republican primary vote.

The Democratic primary is of little consequence because the national party stripped all delegates from the contest as punishment for moving it earlier in the year. Florida Republicans lost half their delegates for doing the same.

Florida is so varied that some say it is several states in one.

“It’s hard to have a singular, unifying message in Florida because you’re talking to different constituencies,” said David Johnson, a Republican strategist and former executive director of the state party. “People in Tampa perceive different problems and situations than people in Miami-Dade.”

All Republican candidates have natural constituencies here:

—The Florida panhandle from Pensacola to Jacksonville is the area most akin to the Old South and the most conservative part of the state. This could end up as fertile territory for former Arkansas Governor Mike Huckabee, who relies on evangelical voters for support.

—The southwestern part of the state around Fort Myers and Sarasota is much like the Midwest, with many retirees. Former Massachusetts Governor Mitt Romney or Huckabee could do well.

—Tampa and Jacksonville have a heavy military presence and large numbers of veterans. McCain, a U.S. Navy aviator and Vietnam prisoner of war, likely will benefit.

—Orlando is a mishmash of people with a strong Puerto Rican community, including some who migrated from New York. Possible advantage: Giuliani, the former New York mayor.

—Palm Beach, Broward County and the Miami area are not only home to Cuban immigrants, but also many Northeastern transplants and retirees. Giuliani and Romney could have an edge there.

Florida is a tough, expensive state to cover—800 miles from Pensacola to Key West, 18 million people, sprawling urban areas and a large rural midsection. The population is about 20-percent Hispanic and 16-percent black. More than 2.2 million voters do not belong to either party and cannot vote in the primary.

Anti-immigration stances that play well elsewhere in the country can hurt a candidate in some parts of Florida, particularly among a Cuban-American population with a high number of Republicans. McCain’s effort to reform laws on illegal immigration cost him heavily with core Republicans in other states. Here, it could help him.

And that is just one of the twists the Republican field has to deal with in the winner-take-all contest for 57 delegates to the party’s national nominating convention from Sept. 1-4 in Minneapolis-St. Paul, Minnesota.

Early on, Romney’s campaign was by far the most organized, snapping up endorsements from several allies of popular former Gov. Jeb Bush. He has spent some $3 million on TV ads but does not have soaring poll numbers to show for it.

During the past week, after floundering for a message, Romney found one that appeared to work—that he has the know-how to turn around the economy and fix a broken Washington. Like other states, Florida is seeing signs of a soft economy, dropping real estate prices and the potential for a dip in tourism.

Giuliani has planted himself and his senior staff and volunteers in the state but his organization may not be as strong as it has been perceived.

The more time he has spent in Florida, the less support he has seemed to get, judging by polls that now point to a close race among McCain, Huckabee, Romney and Giuliani.

Giuliani’s strong-against-terrorism message fell flat as the economy worsened and people focused on financial security instead of national security. His TV ads in Florida have shifted to that focus, but it may be too late. Still, a win would go a long way toward validating his gamble that he could sit out early contests and spring into action in Florida and the multiple contests on Feb. 5, when the delegate count will really start to matter.

McCain sought to build a strong Florida organization but all but pulled out during the summertime collapse of his campaign. Now, back in contention after winning New Hampshire and South Carolina, he has sent staff to Florida and, while money is tight, aides say they have enough for 10 days of TV ads.

Huckabee’s rock-solid socially conservative positions and his workingman appeal may bridge some party factions, and it is quite possible Florida will embrace a former Southern governor with a stellar ability to communicate.

The former Arkansas governor’s murky record on economic issues, however, could work against him. He also has little organization in Florida, and there are far fewer Christian evangelicals in the state than in Iowa or South Carolina.