Crist trails Rubio 47 percent to 44 percent in the survey. The three-point deficit is within the poll's margin of error.
Three months ago, Crist, who had been expected to cruise to the nomination, led Rubio by 15 points. In August, Crist led Rubio by 29 points.
But Florida Republicans have become disenchanted with Crist, who is seen as moderate for his support of President Obama's stimulus package, among other issues. They have rallied instead to Rubio, a darling of the Tea Party movement and photogenic fiscal conservative who has benefitted from a surge in populist anger against the president and his fellow Democrats, as well as incumbents more widely.
A Battle for Senate - And the GOP's Soul
In a general election matchup, Rubio bests likely Democratic nominee Kendrick Meek 44 percent to 35 percent. Crist fares slightly better, beating Meek 48 percent to 36 percent.
"Who would have thunk it?," said Peter Brown, assistant director of the Quinnipiac University Polling Institute, in a release. "A former state lawmaker virtually unknown outside of his South Florida home whose challenge to an exceedingly popular sitting governor for a U.S. Senate nomination had many insiders scratching their heads. He enters the race 31 points behind and seven months later sneaks into the lead."
Crist's struggles with Republicans haven't come simply from his decision to back the stimulus, a choice he may have come to regret. As the Miami Herald notes, his jobs program hasn't spurred hiring, he raised taxes in 2009, and his biggest contributor was accused in a Ponzi scheme. It's been a tough year for a governor who had often been mentioned as the future of the Republican Party.
Mr. Obama's approval rating in Florida, meanwhile, has slipped to 45 percent in the poll, while his disapproval rating is 49 percent. When Crist and the president appeared together in support of the stimulus last February, Mr. Obama's approval rating was 64 percent and his disapproval rating 23 percent.