Florida's 21st congressional district race pits incumbent Republican Brian Mast against Democrat James Martin on newly drawn lines rated Solid Republican by forecasters. Pre-election polling, including a September survey showing Mast ahead by double digits, aligned with the district's R+7 Partisan Voter Index and historical Republican strength in the Treasure Coast and Space Coast areas. Early November 3 results placed Mast near 54 percent to Martin's 45 percent, producing a margin consistent with the market's leading 5-10 percent outcome. Limited third-party votes and the absence of major late developments have kept the implied probability concentrated on that band, with traders assigning low odds to wider or narrower spreads or a Democratic upset. Vote counting in key counties continues to influence final certification.