There has never been an openly non-Christian president of the United States. There has never been an openly atheist senator. God, seemingly, is a rock-solid prerequisite for American political life.

Or it was, until this year.

Early in the 2016 primaries, preacher and former Arkansas governor Mike Huckabee and former senator Rick Santorum – both darlings of the evangelical far right – fell by the wayside. So did Wisconsin governor Scott Walker, the son of a preacher.

Ted Cruz, once the Republican race had thinned, tried to present himself as the last godly man, but was roundly beaten – even among evangelicals – by Donald Trump, a man whose lip service to religion was so cursory as to verge on satire.

Trump may have claimed in a televised debate that “nobody reads the Bible more than me”, but he demurred when pressed to name even a verse he liked. His pronouncements show a lack of any knowledge or interest in faith and its tenets; he once called a communion wafer his “little cracker”.

The boorish Trump is a man at whose megalomaniacal pronouncements any half-hearted glance reveals a belief in, if any god at all, only the one he sees in a mirror. The national exercise in cognitive dissonance required for America’s religious rightwingers to convince themselves that he’s a candidate with whom they have anything in common is truly staggering.

But evangelicals don’t seem troubled. In the March primary in Florida, Trump carried 49 per cent of the evangelical vote. He won Mississippi, a state where fully three-quarters of Republican primary voters are white evangelicals.

In the Democratic primary, Bernie Sanders became the first Jewish candidate ever to win a presidential primary – though he has barely once spoken about his faith – and Hillary Clinton has spoken about god on the campaign trail only occasionally, without receiving much media play. In fact, when the question of faith came up at one Democratic debate there was a backlash against CNN for even asking.

The truth is that Christian faith as a requisite for political power has drooped into a kind of virtue-signalling: the “Jesus Is My Homeboy” bumper-sticker; the crucifix tattoo; the meme on social media about footprints in the sand. It is about identity politics, tribal politics, me-and-mine versus you-and-yours politics, but it hasn’t really been about faith for a while.

What the hell happened?

Partly, there was a demographic shift. “Unaffiliated” is by far the fastest-growing religious category in the US, according to a study by the Pew Research Center, which also showed that the total proportion of Americans who define as Christian dropped almost 9 percentage points between 2007 and 2014.

There is no doubt that America is still a fairly devout nation compared with the UK, but the political mythos that developed around its Christianity is a relatively late invention. The words “under god” were only implanted into the pledge of allegiance – between the words “one nation” and “indivisible” – in 1954, by President Eisenhower.

The ascendance of the political power of the Christian right in America happened in 1979, when a televangelist called Jerry Falwell founded a pressure group called Moral Majority.

Moral Majority’s support for Ronald Reagan was widely credited for his victory in the 1980 election, which in turn secured for them a position at the top table of Republican politics. For three decades, the Christian right was the single most important voting bloc in America.

But its power has been waning for a decade, and there are greater priorities in the American national psyche now.

Trump’s greatest asset throughout the primary was what makes his religiosity or lack thereof immaterial: his authenticity. His lack of a filter, his ability to wriggle free from gaffes which would have felled any other candidate with a simple shrug. This is what not just religious voters, but all of the Republican voting base were waiting for: someone who isn’t pandering, who hasn’t focus-grouped what they want to hear.

They don’t care that he may or may not truly share their belief in god. Almost all voters in this election cycle – including evangelicals, polling suggests – prioritise the economy over values anyway.

On top of that, the Christian right is facing the beginnings of an insurgency from within its own ranks; a paradigm shift in conservatism. A new culture war is beginning, fought by the alt-right, a movement whelped on anarchic message boards like 4chan, whose philosophical instincts lean towards the libertarian and anarcho-capitalist, and to whom the antique bloviation of Christian morality politics means nothing.

Trump doesn’t pander, an approach only made possible by social media, which amplifies his voice six millionfold while simultaneously circumventing the old establishment constructs – like the media – which had previously acted as gatekeepers to power.

The Christian right – now personified in Jerry Falwell Jr and Liberty University, which Falwell senior founded in the Seventies – found itself another of those constructs. They were forced to choose: jump on board the Trump Train or be left behind.

They chose Trump.