Steve Bannon, the failed presidential adviser and alt-right sympathizer, has declared war on incumbent Republicans, particularly Sen. Mitch McConnell. From his perch at Breitbart, Mr. Bannon is vowing to defeat officeholders who back Mr. McConnell as majority leader or who won’t sign onto Mr. Bannon’s populist agenda. So what kind of challengers is Mr. Bannon marshaling for the midterms?
The first House candidate Mr. Bannon has blessed is former Rep. Michael Grimm, who was forced to resign his New York seat in 2015 after…