Today's Kentucky primary is President Trump's biggest test yet of whether his iron grip on the Republican base can hold even as war and inflation batter his national standing. Why it matters: Trump is trying to take out longtime antagonist Thomas Massie in the most expensive House primary in history — a contest that will show whether his iconoclastic brand of libertarian politics still has a place in the GOP. Until now, the seven-term Massie had never faced a serious threat to reelection. Trum