Against all logic, some prominent conservatives continue to promote the absurd proposition that right-wing candidates who fail to win over GOP voters in Republican primaries would magically succeed on November ballots. This assumption enables them to retain a naive faith in the claim that "true conservatives" who can't mobilize their own base to win nominations will somehow triumph in general elections by drawing support from moderates and liberals. Texas Sen. Ted Cruz has most recently voiced this idea. "You know, if you look at the last 40 years, a consistent pattern emerges," Mr. Cruz observed in a July interview with...