**Trader consensus gives Michael Katz a slight edge at 48.5% over John Shulli at 38.5% to win Delaware's Republican U.S. Senate primary on September 15, 2026**, primarily due to Katz's endorsement by the Delaware Republican Party at its April 27 state convention, where delegates showcased party unity by nominating him alongside other candidates. This backing positions the physician and former state senator—who switched from Democrat to Republican—as the establishment choice, while Shulli campaigns as the anti-establishment outsider, criticizing the party's decision on social media. Absent public polls or recent fundraising data, the tight odds highlight a contested primary with GOP base turnout as a key undecided factor months before the vote.