(CBSNEWS) — Donald Trump has returned to the lead in Iowa while Ted Cruz has now surged past Ben Carson into second place. Carson has slipped from a first-place tie into third.

While Iowa's Republicans generally feel Trump is ready to be commander-in-chief, Cruz scores even better on this measure, boosted by support from very conservative and Tea Party Iowans who feel he is ready to assume the post. That's more than say so about Trump, Carson, Rubio and Jeb Bush.

Since last month, Ted Cruz has gained ground -- and Ben Carson has lost ground -- among some key voting groups in Iowa: evangelicals, Tea Party supporters, those who are very conservative and older voters. And while Trump still leads among some of these groups, it's Cruz who is ahead among the very conservative, and Trump leads Cruz by just two points among evangelical voters.

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