(Updates with polls opening)
By Letitia Stein and David Adams
TAMPA, Fla./MIAMI, Nov 4 (Reuters) - Republican Governor Rick Scott, seeking re-election in a deadlocked race against Democrat Charlie Crist, was set to barnstorm Florida as polls opened on Tuesday, with the outcome of the most expensive U.S. gubernatorial contest appearing to hinge on turnout.
From Miami to Pensacola, Scott planned to stump statewide as polls showed him in a dead heat against Crist, Florida's former Republican governor who is seeking the job back as a Democrat.
Both candidates were joined in recent days by national stars: Former President Bill Clinton campaigned for Crist, while Texas Governor Rick Perry and New Jersey Governor Chris Christie, both possible 2016 Republican presidential hopefuls, made appearances with Scott.
Crist is hoping for a large turnout in urban Democrat strongholds of South Florida, while Scott is banking on rural conservative voters in north and central area of the state.
David Johnson, 41, a Miami Beach bartender, highlighted the state's same-sex marriage ban, which Scott has defended.
"I voted for Charlie Crist, of course, because he supports gay marriage," Johnson said.
Almost half of Florida's likely voters may have cast ballots before Election Day, and turnout may beat the 49 percent showing in 2010, when Scott won by 1 percent, or 61,000 votes.
Democrats, who have not won a governor's race in Florida in two decades, hope a ballot drive to approve medical marijuana will improve turnout by liberal-leaning voters.
"Of course I voted for a medical marijuana," said Johnson. "It's a big deal for the state. It should have happened a long time ago but Florida is always last on things like this."
Diane Darby, a 45-year-old Miami Beach accountant, also voted for Crist, albeit reluctantly. "It's unfortunate Charlie Crist isn't really a Democrat," she said. "It's really a vote against Rick Scott."
She said she was also voting for another ballot amendment popular with Democrats, to fund environmental conservation.
The two candidates disagree on issues including same-sex marriage, medical marijuana, Cuba policy and raising the minimum wage.
Voters have endured some 150,000 mostly negative television ads costing more than $81 million, according to the nonpartisan Center for Public Integrity, more than any other state-level races.
Spending in the race for Florida's governor outpaced even the fight for control of the U.S. Senate in most states, the Center for Public Integrity said in a report, without including a final week ad blitz bolstered by nearly $13 million directly from Scott's personal fortune.
Crist accused Scott of being "out of touch" with working Floridians, reminding voters about the Medicare fraud scandal embroiling the hospital group co-founded by Scott, Columbia/HCA.
Republicans painted Crist as an opportunist who left the party to run unsuccessfully for the U.S. Senate as an independent in 2010 before becoming a Democrat in 2012.
"Obviously this election isn't about picking the best and the brightest," wrote Miami Herald columnist and popular author Carl Hiaasen. "It's about picking the candidate who is the least dangerous to Florida's quality of life." (Reporting by Letitia Stein and David Adams. Additional reporting by Zachary Fagenson in Miami Beach.; Editing by Mohammad Zargham and Lisa Von Ahn)