By Kevin Gray

MIAMI (Reuters) - Two prominent Florida Republicans urged their party to tone down its rhetoric on illegal immigration or risk driving away Latino voters who may be a important bloc in this year's presidential election.

The appeals by Senator Marco Rubio and former Governor Jeb Bush came as Republican candidates courted the state's sizable Hispanic vote four days before Tuesday's Florida primary.

"We must admit there are those among us that have used rhetoric that is harsh and intolerable and inexcusable," Rubio said in a speech on Friday at the Hispanic Leadership Network in Miami.

"And we must admit, myself included, that sometimes we've been too slow to condemn that language for what it is," he added.

Rubio, a Cuban-American, joined the ranks of a growing number of Republicans who worry about the party's appeal to Hispanic voters. Polls show hard-line Republican positions on illegal immigration and border control pose a challenge to Republican attempts to win over some Latino voters.

Bush also called for Republicans to temper their comments. "Hispanic people hear these debates and I think you turn them off, it's not a good thing," he said late Thursday.

The Florida primary, the fourth in the state-by-state battle for the Republican presidential nomination, offers Republican candidates their first chance to gauge support among Hispanics.

Whoever becomes the nominee to take on President Barack Obama, a Democrat, will need support from Latinos, the largest and fastest-growing U.S. minority group, in order to win the White House.

While immigration is less of a defining issue among Florida Hispanics compared to others nationwide, the tone of Republican comments have not gone unnoticed by many Latinos.

As Republican candidates crisscross the state, they face an increasingly diverse Latino community whose vote could help define not only Tuesday's Republican primary but the outcome of November's general election in a crucial swing state.

For years, the Hispanic vote in Florida was mostly identified with Cuban-Americans who often voted Republican and whose political views were largely shaped by the Cuban exile community and their opposition to Cuba's Fidel Castro.

But new Hispanic voting blocs have emerged in the state, including a politically important community of Puerto Ricans, the second largest group of Hispanics, and a growing number of South Americas.

Florida is home to the third-largest Latino population in the United States after California and Texas. Latinos represent over 13 percent of Florida's 11.2 million registered voters, according to data from the Florida Division of Elections compiled by the Pew Hispanic Center.

Nearly a third of eligible Hispanic voters in Florida are of Cuban descent, while 28 percent are of Puerto Rican origin, according to the data. Mexican-Americans, who account for nearly 60 percent of Hispanic eligible voters nationwide, represent just 9 percent of Florida voters.

Once consistently Republican voters, Hispanic voters began to shift five years ago as a non-Cuban-American electorate took form, led by the fast-growing Puerto Rican community.

In 2008, Obama won more than half of Florida's Hispanic vote, in part by riding broad support from Puerto Ricans.

Since then, the number of Hispanics registered as Democrats has widened by more than 100,000 voters over those registering as Republicans. As recently as 2006 more Hispanics in Florida declared themselves Republicans.

Puerto Ricans, many of whom are registered Democrats or independents, are on pace to overtake the Cubans as the dominant Hispanic political force in Florida as their numbers grow, said Luis Martinez Fernandez, a history professor at the University of Central Florida.

"The Puerto Rican electorate has already begun to neutralize the Cuban voting bloc," he said.

Immigration is less of a central issue to Puerto Ricans and Cubans than to other Hispanics. Puerto Ricans are American citizens by birth since the island is a U.S. territory. Cubans enjoy special status under U.S. immigration laws and those who reach U.S. soil can qualify for American citizenship within a year.

Fernandez said that Republican positions on immigration were still turning off some Puerto Ricans.

"Even though Puerto Ricans are not that focused on immigration issues, they were very much alienated back in 2008 by the Republican Party's anti-immigration surge," he said. "They are certainly affected by the anti-immigration attitudes."

A poll by Univision/ABC News released this week showed Mitt Romney holding a 15-point lead over Newt Gingrich among Florida Latino Republican voters, with his support coming from both Cubans and Puerto Ricans. Some 35 percent of Hispanic Republicans plan to support Romney, compared to 20 percent for Gingrich.

Romney holds a lead despite having a tougher stance on illegal immigration than Gingrich. Romney has vowed to veto the Dream Act, a proposal that would allow some children of illegal immigrants a path to citizenship.

However, the poll also showed Florida Latino voters would likely support Obama in a head-to-head matchup with either Romney or Gingrich even though the president has seen his support among Hispanics decline over his handling of the economy.

(Additional reporting By David Adams in Miami abd Barbara Liston in Orlando)