The conventional wisdom is that though Ted Cruz can excite the conservative-activist base of the Republican party, he can’t beat Hillary Clinton in a general election. But the recent head-to-head polling tells a different story. Unless your name is George W. Bush, it’s tough to win 270 electoral votes without winning the popular vote. And Cruz is hanging in there against the Democratic front-runner. The RealClearPolitics average puts Clinton at 46.4 percent and Cruz at 43.9 percent; the most recent McClatchy-Marist survey has it a tie. Meanwhile, Donald Trump, the current Republican front-runner, hasn’t led Clinton in any national poll...