Every day, I run into Republican friends who can't stomach a vote for Donald J. Trump but don't know what to do. Vote for Hillary Clinton, who has trouble with the truth, wants to raise taxes and opposes free trade with Asia? Vote for the Libertarian candidate, Gary Johnson, an outlier who once ran a marijuana business and embraces isolationism? Or not vote at all, maintaining a certain purity but allowing others to decide the next president? I faced exactly these choices myself. I have voted for every Republican nominee for president since 1980, but I will not this time....