House Speaker Mike Johnson has the fate of a democracy and a people in his hands. It’s not the United States, which will survive – even if the coming general election results in another existential test for the constitutional system. The country Johnson has the power to save is Ukraine, two years after Russian President Vladimir Putin invaded, decreeing that it didn’t have the right to exist. Ukraine’s soldiers – trapped in a World War I-style hellscape of trench warfare – are running out of bullets. There are signs that Russia may be about to break a stalemate and tip...