But chipping away at Carson is harder. There is no record to attack. Republican voters seem unfazed by his lack of experience, and his calm, genial manner plays well in Iowa.

About 30 percent of Carson’s evangelical supporters pick Cruz as their second choice, says Ann Selzer, the Iowa pollster who conducted the survey, while noting that the former head of pediatric neurosurgery at Johns Hopkins is viewed favorably by almost all Iowa Republicans. “Cruz’s big target is Carson,” she said. “But the problem is there’s almost no one that doesn’t like Ben Carson. Cruz attacks him at his peril.”
That’s also the view of Jamie Johnson, an evangelical pastor from Boone, Iowa who supported former Texas Governor Rick Perry until he dropped out of the race last month. “Those evangelicals who care most about ideology are with Cruz while those who care about likability are with Carson,” Johnson said, adding that “the social fabric and culture of Iowa is based on likability.”

The Cruz camp acknowledges the Carson surge but predicts it’ll recede under the tougher media scrutiny that comes with improved poll numbers.