Back-to-back polls in recent days show that Iowa’s strong cohort of evangelical voters is, for now, casting its lot with Ben Carson, a retired pediatric neurosurgeon, over Trump. While polls routinely fluctuate, Trump has had an unusually lengthy run at the top of the heap, besting more than a dozen GOP rivals.

But conservative Republican voters may be sounding the first alert that rural Iowa, very far away from billionaire Trump’s glittery New York City bastion, may become the candidate’s Waterloo. Some 28% of those surveyed in a Des Moines Register/Bloomberg politics poll this week favored Carson. That was ahead of Trump’s 19%.

This may be a reflection of the cultural gulf between tractors and private jets, or it may be that Carson’s resolute Christianity edges out Trump’s newly acquired spirituality. Trump is carrying a Bible these days and professing to be a believer, in addition to having the necessary force to “make America great again.”

Compared to Trump, Carson is certainly more amiable and soft spoken, both solid Midwestern virtues. An African-American surgeon with impeccable medical credentials from his career at Baltimore’s renowned Johns Hopkins University, Carson has no hesitation, though, in expressing isolationist, and often inflammatory, views. He has said the country is on a wrong path, modeling its health care system on slavery and its foreign policy on communism.

No matter the accuracy of his views, his low-key approach has won over evangelical voters who, as recently as August, had given Trump the thumbs up over Carson, 23% to 18%.

A big boost in Carson’s support came from women, who helped push him ahead of Trump, and over two other trailing candidates, Marco Rubio of Florida and Ted Cruz of Texas, both of whom are sitting U.S. senators. Hawk Eye voters had little interest in once evangelical favorites like Mike Huckabee and Rick Santorum, both of whom are stuck in the political doldrums, according to polls, despite their Christian credentials.

The Des Moines Register poll’s findings came on the heels of another from Quinnipiac University, where women were sharply in favor of Carson over Trump, siding with him by 20 points, 33 to 13. Men were almost evenly split, with 25% backing Carson and 24% choosing Trump.

Some 30% of people who say they are likely to participate in the Iowa Republican Caucus said they “would definitely not support” Trump for the Republican presidential nomination. As for Jeb Bush, who is often cited as the choice of the traditional Republican establishment, 21% of participants said that there is “no way” they would support him for the nomination.

While most of the 574 poll participants said Carson is better equipped to handle social issues, they chose Trump by significant margins on the economy, taxes, and illegal immigration. Those questioned split closely on which of two top candidates would best handle foreign policy.

About one third of those questioned said the key issue in their backing was a candidate’s support for their values, and slightly fewer, 23%, said they wanted a candidate who is honest and trustworthy. Those qualities tipped the balance for Carson, who, according to 84% of participants, shares their values, and who, according to 89%, is honest and trustworthy.

Only one-third of those questioned said they believed Trump is a committed Christian.

To bolster his Christian bona fides, Trump, in a campaign appearance in Burlington, Iowa, this week, promised to rid use of the expression “happy holidays” to refer to the end-of-the-year holiday period.

“I’m a good Christian,” he told a rally, according to CNN. “If I become president, we’re gonna be saying Merry Christmas at every store.”