Then-Republican presidential candidate Donald Trump railed against “so-called Christians” and “pieces of s—” evangelicals who supported Sen. Ted Cruz (R-Texas) in the 2016 Iowa caucuses, according to a forthcoming book. At the time, allies of Cruz had been making hay of Trump’s flub before an audience at Virginia’s Liberty University, a conservative evangelical college, in which he botched a question about his favorite Bible verse and replied that it came from the book of “Two Corinthians,” rather than “Second Corinthians.” “The laughter and ridicule were embarrassing enough for Trump,” Tim Alberta writes in his new book, “The Kingdom, the Power,...