Incumbent Democrat Suzan DelBene faces Republican Mary Silva in Washington's 1st Congressional District on November 3, 2026. The district's D+15 partisan lean and DelBene's strong primary performance, where she captured over 54% of the vote, underpin the market's pricing across Democrat margin buckets and Republican win probabilities near 38%. Forecasters rate the seat Solid or Safe Democratic, consistent with historical results in this northern Seattle-area constituency. Limited recent polling and the absence of major late-cycle developments keep the exact margin of victory dispersed across multiple outcomes in trader assessments. Scheduled events such as candidate debates or national midterm dynamics could still influence final vote shares within the resolution window.