Ted Cruz’s campaign isn’t about constitutional principles; it’s about ambition. In his three years in the Senate, he has helped to engineer a shutdown of the government and has alienated virtually the entire chamber, both of which he bills as accomplishments since he lacks real ones. Now, whether he’s threatening to “carpet bomb” Syrian villages or pitching a phony “flat tax” that would batter middle-class consumers, Mr. Cruz will say anything to win. The greater worry is that he’d follow words with action.

More than a half-dozen other candidates are battling for survival. Jeb Bush has failed to ignite much support, but at least he has criticized the bigotry of Mr. Trump and the warmongering of Mr. Cruz. Senator Marco Rubio, currently embracing the alarmist views of the front-runners, seems to have forgotten his more positive “New American Century” campaign, based on helping the middle-class. The terrorist attacks in Paris and San Bernardino exposed Ben Carson’s inability to grasp the world. Gov. Chris Christie of New Jersey has said he would shoot down Russian planes, engage with the dead king of Jordan and bar refugees, including orphaned Syrian toddlers.