Rick Scott, the multi-millionaire former hospital chain executive, had trailed in recent polling, but defeated Florida Attorney General Bill McCollum 46-43 after a campaign that turned ugly in recent weeks.
In the other hotly contested and nationally scrutinized Florida race, Jeff Greene, the insurgent billionaire who poured tens of millions of his own money into the Democratic primary was unable to defeat Rep. Kendrick Meek, a South Florida lawmaker with a political pedigree. Meek got more than 57 percent of the vote.
"The pundits thought this seat could be bought," Meek said in a message to supporters. "Our critics wrote us off."
Meek will face off against Republican Marco Rubio, the Tea Party favorite and former State House speaker, whose strong conservative candidacy drove moderate Gov. Charlie Crist out of the Republican party earlier this year when his public backing of President Obama's economic policies made him unpalatable to Florida Republicans.
Rubio faced only token opposition in the Republican primary.
But Crist has stayed in the Senate race as an independent, setting up a three-way contest in November.
Despite campaign help for Meek from former President Bill Clinton and President Obama, some Washington Democrats had secretly been hoping for Greene to pull out a victory because it would have helped Crist, who they hope could help them maintain their majority in the Senate.
Recent polling shows Rubio and Crist neck and neck, with Meek drawing between 15 and 20 percent of votes in a hypothetical general election.
"While Meek is an unabashed liberal, Gov. Charlie Crist has made it clear that he will simply say or do anything to win an election, as his positions seem to move wherever the most politically expedient wind blows," said Sen. John Cornyn, R-Texas, who chairs the National Republican Senatorial Committee in a memo previewing their argument for Rubio leading into the fall.
Greene's brief candidacy provided salacious story lines; he brought a big personality into the race and was dogged by, among other things, his personal friendship with the former boxer Mike Tyson, who was the best man at Greene's wedding, and his former roommate Heidi Fleiss, notorious as the Hollywood Madame.
Then there's his yacht called the "Summerwind," where there may or may not have been scandalous parties in far-flung and exotic locations.
Rick Scott, who like the billionaire Greene, who bankrolled much of his own primary campaign and spent $50 million of his own funds, narrowly defeated Florida Attorney General Bill McCollum.
The race has veered both candidates to the right. Scott, who became a national figure when he organized a group that spent millions opposing the passage of Democrats' Health Reform Law, he unveiled an immigration proposal that would be even stricter than the controversial Arizona law that requires immigrants to carry proof of legal residency.
But Scott has struggled to distance himself from a massive $1.7 billion Medicare fraud fine -- the largest ever -- levied against the Columbia/ HCA health care company, when he was CEO.
Florida CFO Alex Sink, who easily won the Democratic primary, had stayed above the fray, but whomever she meets in November will be bloodied by the primary and ready for a fight.
The five-way Democratic race for Vermont governor, the most contested race in the state, is too close to call.