Cruz has the decibel part mastered and has moved rightward on immigration in an attempt to sew up conservative support. “He goes where he needs to go,” one Republican strategist told me. Influential and obstreperous Rep. Steve King has endorsed Cruz; influential evangelical Bob Vander Plaats seems about to. Cruz has benefited in one way from the Trump ascendency. He looks positively reasonable in comparison. And Cruz doesn’t have Trump’s main drawback in reaching out to conservatives — that Trump isn’t actually a conservative.

Rubio is gaining steam in Iowa on the strength of a perception that his next-generation conservatism matches up well against Clinton’s old-time liberalism. He seems to be on just about everyone’s top-three list. But the Iowa caucuses are not won by being a fallback choice. Rubio is trying to gain ground by moving right. During recent visits, he has emphasized his role as a conservative revolutionary — which is not easy for anyone once part of the immigration-reform Gang of Eight. And since then he has also moved rightward on immigration, demonstrating how Trump’s nativism has pulled many in the GOP toward restrictionism.

Rubio’s strategy is not without risk. Heading off Cruz on the right may come across as forced and inauthentic. And siding with anti-Branstad forces in Iowa could cause the Terry Branstad Republicans to coalesce around Christie or Bush. This seems to be the only possibility for Bush to finish a respectable third or fourth. And the calculations of all the candidates appealing to evangelicals are complicated by Carson — whose autobiography, “Gifted Hands,” is sometimes used as a textbook by homeschoolers. He is slipping but probably not collapsing.