Influential American evangelical magazine Christianity Today has denounced Donald Trump and Christians who would vote for him in a scathing editorial.

"Evangelicals, of all people, should not be silent about Donald Trump's blatant immorality," wrote the magazine's executive editor, Andy Crouch, yesterday (11 October).

"He wantonly celebrates strongmen and takes every opportunity to humiliate and demean the vulnerable," Crouch continued, criticising Trump's support for Russian President Vladimir Putin. "He shows no curiosity or capacity to learn. He is, in short, the very embodiment of what the Bible calls a fool."

The magazine, founded by renowned 97-year-old American evangelical preacher Billy Graham six decades ago, describes itself as having a global reach to influence church ministers and shape evangelical Christian opinion.

Throughout the 2016 presidential campaign Trump has said that he can rely on "the evangelicals" for support. A July poll showed that he could rally the vote of as many as 78% of white evangelicals — even more than Republican contender Mitt Romney in 2012. The latest national polling average shows Clinton with 45% and Trump with 40% of the vote.

Early this month, Real Clear Politics revealed that since 2011 about $286,000 (£233,100) from the Donald J Trump Foundation has flowed to Christian organisations, such as the Palmetto Family Council. Although, the report makes clear that Trump did not ask for favours in return for his donations.

Throughout his campaign Trump has taken up the causes evangelicals hold most dear, including speaking against same-sex marriage and pushing changes to abortion law to revoke public funds for the procedure.

But a video that emerged last Friday showing Trump's "vile and crude boasting about sexual conquest – indeed, sexual assault" is a step too far, said Crouch. The video is an out-take from Access Hollywood in which Trump describes forcing himself on a married woman and grabbing women by their genitals. It, and other revelations about Trump's past, Crouch insisted, has caused evangelical leaders to reconsider their vote.

Even so, prominent evangelicals such as Pat Robertson and Jerry Falwell Jr have stood by the candidate amid the controversy.

The editorial also didn't spare Democratic nominee Hillary Clinton. Contending that she has "pursued unaccountable power through secrecy" by maintaining a private email server while Secretary of State, Crouch criticised her private speeches to Wall Street, stating they show she is embedded with the "most powerful representatives of the world system".

Nevertheless, Crouch warned his evangelical readers that voting for Trump would ally them "with someone who violates all that is sacred to us" in a "vain hope given his mendacity and record of betrayal" that he will champion their causes.