The evangelical support for Republican candidate Donald Trump might not be as high as is being assumed, new research suggests.

According to top pollsters Gallup, backing for Trump is actually below average among religious Republicans. 

Instead it is retired neurosurgeon Ben Carson who is favourite among the most devout, with Trump lying a poor 12th among the 17 Republican candidates. Ahead of Trump are Mike Huckabee, Marco Rubio and Ted Cruz, in second, third and fourth positions. 

"No sign here of any special appeal on the part of Trump to highly religious Republicans," says Frank Newport in his Gallup opinion piece, noting that Carson's 56-point net favorable among the highly religious Republicans is more than two-and-a-half times higher than Trump's. Huckabee, a former Southern Baptist minister, is the most skewed toward the highly religious Republicans of any of the candidates.

Russell Moore, president of the Ethics and Religious Liberty Commission of the Southern Baptist Convention, criticises evangelicals who are backing Trump. Writing in the New York Times he says: "To back Mr Trump, these voters must repudiate everything they believe." He questions what happened to their commitment to traditional family values.  Baffled by those who argue in support of Trump, Moore says the problem is not just Trump's "personal lack of a moral compass", admitting that he is, after all, a casino and real estate mogul who has built his career off gambling. Moore adds: "He's defended, up until very recent years, abortion, and speaks even now of the 'good things' done by Planned Parenthood. In a time when racial tensions run high across the country, Mr Trump incites division, with slurs against Hispanic immigrants and with protectionist jargon that preys on turning economic insecurity into ugly 'us versus them' identity politics. When evangelicals should be leading the way on racial reconciliation, as the Bible tells us to, are we really ready to trade unity with our black and brown brothers and sisters for this angry politician?"

Further signs that support for Trump might be on the wane came after the end of the marathon three-hour CNN debate, when the front-runner was criticised by influential commentators for being "low energy". Glenn Thrush of Politico wrote: "The Trump joy ride is over, and the race looks to get a lot more competitive as he tries to transform his castle made of bombast into a truly functional campaign."