Democrats could show some strength in Florida, where one Republican-held seat is already ranked as a toss-up by CNN. GOP Rep. Carlos Curbelo is in danger of losing his seat composing the southern tip of the state. GOP Rep. Ron DeSantis is running for governor, and fellow GOP Rep. Dennis Ross is retiring. CNN ranks these seats -- as well as that of Republican Brian Mast -- as likely Republican. Democrat Bill Nelson faces a tough re-election to the Senate against Republican Gov. Rick Scott, who announced his run in April and has deep pockets. CNN rates this as a toss-up, and it will likely be one of the most expensive Senate races of the cycle.