Brian Mast holds an 86.5% implied probability as the FL-21 winner due to his incumbency, substantial fundraising edge exceeding $2.8 million in cash on hand, and the district’s Republican lean after recent redistricting. James Martin, the Democratic challenger and Coast Guard veteran who narrowly won his August primary, trails at 13.6% amid limited resources under $83,000 and lower name recognition. A late September poll initially showed Mast ahead before tightening after candidate information, yet broader forecasts rate the race Likely or Solid Republican with Mast favored by double digits. Traders weigh these structural advantages and the November 3 general election timeline against any national environment effects.