WASHINGTON - A three-way race for an open Senate seat in Florida will test the ability of a popular governor running as an independent to overcome Republican and Democratic rivals in a campaign that will help determine which party controls the Senate. Gov. Charlie Crist, who left the Republican Party in the face of a challenge from Marco Rubio, a former state House speaker, must peel votes from his old party as well as from Democratic nominee Kendrick Meek, a black Miami congressman, to win the Senate seat. Florida voters will also choose Crist's successor in a gubernatorial contest between two former business executives: Democrat Alex Sink, the state's chief financial officer and onetime president of Bank of America's Florida unit, and Republican Rick Scott, a former head of Columbia HCA Healthcare Corp. Scott spent millions of his own money to beat Attorney General Bill McCollum in Tuesday's Republican primary. Intensive spending and advertising boosted Scott, a political novice, in a bruising primary battle with McCollum, who served for two decades in Congress before running for statewide office. The fractious primary race may benefit Sink, also a relative newcomer after serving one term in public office following a career in banking. In the Senate race, Crist is campaigning as an independent after bolting the Republican Party. Republican Rubio is backed by Tea Party activists. This leaves Meek to court the Democratic base in a swing state where Democrats outnumber Republicans, yet independents often settle election contests. 'I am the real Democrat in this race,' Meek told cheering supporters after he defeated billionaire real-estate investor Jeff Greene. 'I am running against two conservative candidates' and am 'the only candidate who opposed offshore drilling' before the April 20 explosion of BP's oil rig in the Gulf of Mexico, he said. Rubio, 39, who won the Republican Senate nomination Tuesday, said the country is going the wrong way. 'If you like the direction that America is headed, if you think Washington is doing the right thing, there are two other people on the ballot and you should vote for them,' he told supporters after winning his primary. He promised to 'offer a compelling vision of the future' for the nation. Crist said he was an alternative to candidates 'imprisoned by the parties' that support them. 'If you want somebody who is on the hard right, you have a candidate,' he said on CNN's 'Larry King Live.' 'If you want someone on the hard left you have a candidate.' In an election year that will hinge on voter enthusiasm, the Florida Republican turnout was almost 50 percent higher than that of Democrats. More than 1.2 million Republicans cast ballots in the party's gubernatorial primary compared with about 900,000 in the Democratic Senate primary. 'The enthusiasm gap is evident,' said Susan MacManus, a political scientist at the University of South Florida in Tampa. The three candidates are vying to fill the Senate seat vacated last year by the resignation of Mel Martinez, a former Republican National Committee chairman. Crist appointed a former chief of staff, George LeMieux, to fill the vacancy. Crist, 54, who served as a state legislator and Florida attorney general before becoming governor in 2006, dropped out of the Republican Senate primary and filed to run as an independent after polls showed Rubio winning the nomination. Crist was an early supporter of the $816 billion economic- stimulus program that President Barack Obama pushed through Congress last year against broad Republican opposition. He also campaigned against offshore oil drilling after the BP rig explosion in the gulf. 'Crist has come up in the polls running as a Democrat,' MacManus said in an interview with Bloomberg Radio. Looking at the general election ahead, Crist led Rubio 39 percent to 32 percent in a Quinnipiac University poll of 1,096 registered voters, with Meek getting 16 percent. The poll conducted Aug. 11-16 had a 3-point error margin. Rubio has tacked to the center to try to appeal to more moderate voters, 'but not on issues that are vital to Republicans' such as cutting government spending and taxes, MacManus said in a telephone interview. 'Debt is a big issue here' and 'has showed up in the polls as a huge driver of how people are thinking about things,' she said. Meek, 39, who served in both Florida's House and Senate, succeeded his mother, former Representative Carrie Meek, with his election to Congress in 2003. Former President Bill Clinton stumped for him in the Senate primary, criticizing Greene's use of his own fortune to bankroll his candidacy. Florida's jobless rate -- 11.5 percent last month -- and third-highest mortgage- foreclosure rate after Nevada and Arizona have generated anxiety about the economy among voters. 'People in Florida are very upset at the administration; they are very upset at the stimulus package,' said Dario Moreno, a political scientist at Florida International University in Miami. 'These are the kinds of things that propelled these two outsiders,' he said of Scott and Greene. 