Michael Katz holds an 81% implied probability in the Delaware Republican Senate primary market due to his dominant performance at the state party convention in late April 2026, where he secured roughly 82% delegate support and the official GOP endorsement. This institutional backing from party leaders has translated into additional recent endorsements, including from Delaware College Republicans, reinforcing his frontrunner status ahead of the September 15 primary. John Shulli, an Army War College instructor running as the main challenger, has raised substantially more campaign funds but lacks comparable party infrastructure or grassroots momentum within Republican circles. Traders appear to view the convention result as the decisive early signal in this low-profile race, consistent with historical patterns where endorsed candidates consolidate support quickly in small-state primaries.