The fight for the Republican nomination for the U.S. Senate is shaping up as U.S. Rep. Connie Mack IV's to lose.

Mack has opened a huge lead over his rivals in a three-way contest in a poll released Thursday.

Mack was preferred by 40 percent of 742 registered Florida Republican voters in a recent random telephone survey compared to 8 percent for Tea Party favorite Mike McCalister. Fort Lauderdale attorney George LeMieux, who served the final 16 months of former U.S. Sen. Mel Martinez's term, was favored by 7 percent. Forty-one percent were undecided.

The Quinnipiac University survey of Republican voters taken May 15-21 has a margin of error of plus or minus 3.6 percentage points.

The GOP winner faces incumbent U.S. Sen. Bill Nelson in November.