TOPEKA, Kan. (AP) — Republicans brimmed with newfound confidence Wednesday about keeping an open Senate seat in Kansas after establishment-backed Rep. Roger Marshall won the party's nomination, advancing to face an unusually formidable Democrat in a tough year for the GOP.

Marshall's first tasks were quickly refilling his campaign treasury and rebuilding Republican unity after an often-bitter primary campaign. But he and other Republicans immediately previewed the fall campaign in which they are expected to use the threat of Democrats capturing a Senate majority to try and blunt Barbara Bollie...