Jeff Merkley's incumbency as Oregon's longtime Democratic U.S. Senator anchors his 97.5% trader consensus on Polymarket for the Democratic Senate primary winner. Recent polls, including a DHM Research survey showing him at 78% against Jacob Ryan's 11%, underscore his dominance, fueled by robust fundraising exceeding $5 million and endorsements from state Democratic leaders. Absent major challengers or shifts since filing deadlines, traders price in low upset risk ahead of the May 21 primary. Realistic scenarios disrupting this include a damaging scandal surfacing or unexpected progressive mobilization boosting Ryan, though no such catalysts have materialized.