Last Sunday night in Miami, Arizona Senate hopeful Blake Masters dropped by the waterfront mansion of top Republican fundraiser Keith Rabois to deliver a closing pitch to 40 G.O.P. donors. Some enjoyed risotto while trying not to fall into a nearby pool. Others chatted up Tucker Carlson’s videographers, who told attendees they are working on a documentary about the race. Then Masters made his way to the garden to speak. Dressed in a long-sleeve brown t-shirt and grasping a wireless microphone, Masters launched into his usual spiel—tearing down Democratic incumbent Mark Kelly and lamenting that two-parent families can’t get by on a single income anymore—before a donor interjected during the Q&A with a more provocative prompt: Why is the Republican establishment letting him twist in the wind? 

Masters, after all, is in a vise. Mitch McConnell’s political allies believe the current polling shows he “doesn’t have a shot” of defeating Kelly in November, a person familiar with their thinking told me, which is why the the Senate Leadership Fund, McConnell’s super PAC, recently redirected $8 million in planned September ad spending to more winnable races. McConnell’s mandate, after all, is to secure a 51-seat Senate majority for the G.O.P., not to support seemingly longshot Republican candidates.