The extent to which evangelical leaders' support will continue to influence who occupies the White House after Donald Trump was tested today after senate candidate Mitt Romney of Utah said that Baptist minister Robert Jeffress should not be giving the opening prayer at the opening of the new US embassy in Jerusalem because he's a 'religious bigot'.

The former Massachusetts governor and 2012 Republican presidential nominee attacked Jeffress for his remarks about Jews, Mormons and Islam.

Romney wrote on Twitter: 'Robert Jeffress says "you can't be saved by being a Jew," and "Mormonism is a heresy from the pit of hell." He's said the same about Islam.'

Jeffress responded, also on Twitter, saying: 'Historic Christianity has taught for 2,000 years that salvation is through faith in Christ alone. The fact that I, along with tens of millions of evangelical Christians around the world, continue to espouse that belief, is neither bigoted nor newsworthy.'

The row has led the conservative commentator Todd Starnes to lash out at Romney.

Starnes pointed out that the North American Mission Board of the Southern Baptist Convention labels the Church of Jesus Christ of Latter-Day Saints, to which Romney belongs, as 'cultic'.

NAMB states: 'Mormon teaching is not orthodox nor biblical in that it does not hold to the inerrancy of Scripture, nor to the full, eternal divinity of Christ. On those two points alone, Mormon teaching does not qualify as orthodox Christianity.'

Starnes concluded: 'The question must be asked — does Romney consider the 14 million members of the Southern Baptist Convention to be religious bigots, too?'

To be fair to Romney, he clearly had no intention of insulting all Southern Baptists, and there is plenty that Jeffress has said that could single him out for special criticism of his own.

Romney has form when it comes to courageously attacking Trump too, including a comprehensive take-down in 2016.

Back then, he attacked Trump's economic and foreign policies before saying: 'Think of Donald Trump's personal qualities, the bullying, the greed, the showing off, the misogyny, the absurd third grade theatrics. We have long referred to him as "The Donald." He is the only person in America to whom we have added an article before his name. It wasn't because he had attributes we admired.

'Now imagine your children and your grandchildren acting the way he does. Will you welcome that? Haven't we seen before what happens when people in prominent positions fail the basic responsibility of honourable conduct? We have, and it always injures our families and our country.'

Romney survived that controversy, when Trump was more popular than he is now, but whether he can emerge as a Republican presidential candidate again after his calling Jeffress a 'bigot', remains to be seen.

It appears that in the current climate, you mess with the SBC — and evangelicals — at your peril.