Michael Katz secured the Republican nomination for Delaware's U.S. Senate seat in the September 15, 2026 primary, defeating John Shulli by a wide margin of roughly 77% to 23% after polls closed. As the Delaware Republican Party's endorsed candidate, Katz benefited from stronger name recognition as a former state senator, greater fundraising, and established business and medical credentials that appealed to primary voters in a low-turnout contest. Shulli's campaign, backed by figures such as former National Security Advisor Michael Flynn, failed to close the gap despite his military background. The outcome reflects the party's preference for a candidate with prior elective experience in the state. Potential challenges to this result remain limited, primarily to any unforeseen legal disputes over vote certification or an unexpected withdrawal before the general election against incumbent Democrat Chris Coons.