MIAMI (Reuters) - The top four Republican candidates for president are in a statistical tie in Florida, where Democrat Hillary Clinton holds a 21-point lead over Barack Obama for their party’s nomination, according to a Quinnipiac University poll released on Monday.

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Among Republicans likely to vote in Florida’s January 29 primary, Arizona Sen. John McCain has 22 percent followed by former New York City Mayor Rudy Giuliani at 20 percent. Former Massachusetts Gov. Mitt Romney and former Arkansas Gov. Mike Huckabee stand at 19 percent each, the independent poll said.

The gap among all four was within the poll’s error margin of 4.8 percent.

Former Tennessee Sen. Fred Thompson has 7 percent of likely Republican primary voters and Texas Rep. Ron Paul has 5 percent, the poll said.

“The Republican race is a dead heat with all four major contenders within three points for first place,” said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

Republicans and Democrats are waging a state-by-state fight to win their parties’ nomination to compete in November’s election to succeed President George W. Bush. The Florida primary is one of four state contests later this month.

The poll of 419 Republican voters likely to take part in the selection of the party’s presidential candidate and 421 Democratic voters likely to vote in that primary in Florida was conducted from January 9 to 13.

McCain, fresh from a victory in New Hampshire’s nominating contest, showed the largest movement since the last Quinnipiac poll on December 20, gaining 9 percentage points from his fourth-place 13 percent showing.

Giuliani, who has pinned many of his presidential hopes on the Florida primary after largely ignoring Iowa and New Hampshire and showing poorly in each, has lost 8 percentage points from his then-first-place 28 percent in the December survey.

“These numbers can’t be good news for Mayor Giuliani who has staked his entire campaign on winning Florida and whose lead has evaporated,” Brown said. “McCain’s jump is not unexpected given his New Hampshire victory,” he added.

Among Democratic likely voters, Clinton leads Obama 52 percent to 31 percent, a margin virtually unchanged from December. Clinton, a New York senator who would be the first woman president, held an even wider lead among women voters.

Former Sen. John Edwards was the big loser, dropping to 9 percent in January from his 19 percent showing in December.

Clinton’s lead looked more solid, with 75 percent of Clinton voters saying they were unlikely to change their minds. Only 61 percent of those supporting Obama, an Illinois senator who would be the first black president, said they felt that way.