When Sen. Ted Cruz (R-Tex.) capitulated last Friday and announced his intention to vote for Donald Trump, it marked a key shift in the presidential race. Cruz was the highest-profile holdout from the Trump train, having weathered boos and scorn at the Republican convention in defense of his ideals. But the shift that was marked was more broadly was that Cruz was simply part of a wave. Other Republican holdouts have come on board — and that's a large part of why the race has gotten so close.