10. Marco Rubio
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Campaign Contributions: $11,564,046
Former state House Speaker Marco Rubio has the backing of the Tea Party and, according to the polls, is currently in a dead heat with Florida Gov. Charlie Crist. Experts say competition from Rubio pushed Crist to become an independent; Crist might have lost the GOP nomination had he not quit the GOP. Now, Rubio, Crist and Democratic U.S. Rep. Kendrick Meek head into a three-way November matchup. Rubio, a conservative, has painted Crist as catering to the Obama agenda, but he will need to gain the support of moderate Republicans and independents to win.