Mitt Romney has opened up a nine-point lead on Newt Gingrich in a new Florida poll released Friday, just four days before the Sunshine State's primary to choose the Republican presidential nominee.

The Quinnipiac University survey showed Romney, once seen as a shoo-in to take on Democratic US President Barack Obama, leading 38-29 percent over former House of Representatives speaker Gingrich among likely Republican voters.

Only six percent of those polled were undecided, but 32 percent said they might change their mind by Tuesday, when Florida votes in a winner-take-all race for 50 delegates.

The Quinnipiac poll suggested former Massachusetts governor Romney has stopped the rot and addressed doubts over his credentials after an embarrassing loss to Gingrich in the South Carolina primary, where he had once led strongly.

A loss in Florida would leave Gingrich's bare-bones campaign with an uphill struggle to reach the 1,144 delegates needed to win the nomination as the race opens out into multiple states.

"Newt Gingrich's momentum from his South Carolina victory appears to have stalled and governor Mitt Romney seems to be pulling away in Florida," said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

"Romney also has a better favorability rating from likely primary voters, which supports his lead in the horse race. Of course, with four days before election day, there is time for another reversal."

The Quinnipiac survey was taken between January 24-26, before Romney turned in a strong debate performance in Florida on Thursday night that repeatedly left Gingrich on the defensive in their final showdown ahead of the primary.

The latest poll was taken among 580 Republicans who were likely to vote on Tuesday. The margin of error was plus or minus 4.1 percentage points.

The latest survey compares to results of a January 25 poll by Quinnipiac that showed Romney with 36 percent in Florida to Gingrich's 34 percent.

It showed that men back Romney 36-29 percent, a shift from January 25, when they favored Gingrich 37-33 percent. Romney leads 40-30 percent among women, virtually unchanged.

Texas congressman Ron Paul, who has done virtually no campaigning in Florida, was on 14 percent, and former Pennsylvania senator Rick Santorum was in fourth place, with 12 percent, the survey said.