Incumbent Republican Brian Mast faces Democratic nominee James Martin in Florida's 21st congressional district, a seat rated solid or safe Republican by major forecasters following Mast's 61.8% win in 2024. Trader consensus clusters on a Republican margin of 10-15 points because the August Democratic primary between Martin and Bernard Taylor was decided by fewer than 400 votes, providing little signal on general-election strength. Limited public polling, modest Democratic fundraising, and the absence of major recent campaign developments keep probability estimates for specific margin buckets tightly grouped. Scheduled events such as candidate debates, new polling releases, or shifts in Treasure Coast turnout could quickly widen spreads among the Republican margin outcomes or the low-probability Democrat-wins bucket.