WASHINGTON — Senator John McCain, the sometimes cantankerous, often charming and eternally irrepressible Republican from Arizona, has never minced words. But in the twilight of a long and storied career, as he fights a virulent form of brain cancer, the 81-year-old senator has found a new voice.. In twin speeches — one in July, where he issued a call to bipartisanship in the Senate, and another in Philadelphia this past week, where he railed against “half-baked, spurious nationalism” — Mr. McCain has taken on both his colleagues and President Trump. In the process, his friends and fellow senators say, he...