(CNN) Florida's coming US Senate showdown is already set, so the real drama Tuesday in the Sunshine State centers on a pair of gubernatorial primaries with national implications for both parties.

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For Republicans, the candidate backed by President Donald Trump appears to have the advantage. Florida Democrats, meanwhile, believe they are finally on course to end two decades of Republican rule after losing each of the last two governor's races by a single percentage point.

First, though, they have to choose a nominee.

The Democratic primary has been expensive, with more than $100 million in spending, and messy, as a competitive field of five settled into what most expect to be a three-horse race on Tuesday.

Former Tallahassee US Rep. Gwen Graham -- the only woman in a field she described once as "Gwen and the men" -- enters primary day with a small but seemingly durable lead in the polls over her two strongest opponents, former Miami Beach Mayor Philip Levine and Tallahassee Mayor Andrew Gillum.

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