What has happened to members of the “Moral Majority”? You remember them, right? The conservative evangelicals who helped deliver victories for “born again” Republicans Ronald Reagan and George W Bush and pushed for the impeachment of the philandering Democrat Bill Clinton? How come these “values voters” seem to have lost all their, ahem, values?

Consider the results of two surveys conducted by the Public Religion Research Institute (PRRI). In 2011, fewer than one in three white evangelical Protestants said an elected official could behave ethically in their public life, if they had committed moral transgressions in their private life.

Yet just five years later, in 2016, more than seven in ten white evangelical Protestants said a politician’s personal morality did not matter to them.

“No group has shifted their position [on this issue] more dramatically than white evangelical Protestants,” observed the PRRI. “Today fewer than half (49 per cent) of white evangelical Protestants say it is very important that a candidate have strong religious beliefs, while nearly two-thirds (64 per cent) expressed this view in 2011.”

US evangelicals have gone from being obsessed with the personal lives of politicians to, basically, not giving a damn. Why? Donald Trump. Evangelicals lined up behind the former reality TV star in their tens of millions. These were not reluctant supporters, opting for the lesser of two evils. They were hardcore fans who cheered at campaign rallies and whose pastors offered full-throated endorsements of Trump.

In January 2016, prominent evangelical Jerry Falwell Jr compared Trump to Christ, claiming the billionaire property tycoon lived “a life of loving and helping others, as Jesus taught”. “You inspire us all,” televangelist Pat Robertson told Trump in February 2016. Franklin Graham, son of renowned evangelist Billy Graham, even suggested that “it was the hand of God” that helped Trump defeat Hillary Clinton.

We can agree to disagree on whether it was the hand of God – or even the hand of Vladimir Putin – that put Trump in the White House but what is beyond doubt is that evangelicals played a major role in his unexpected victory. Eight in ten white evangelical Protestants voted for Trump in 2016. It was a truly remarkable feat: according to a study by Pew, “Trump’s 65-percentage-point margin of victory among voters in this group… matched or exceeded the victory margins of George W Bush in 2004, John McCain in 2008 and Mitt Romney in 2012.”

To call Trump, as a recent Reuters report did, “an unlikely torchbearer for conservative Christians” is an understatement. How is it not anything other than brazen hypocrisy for evangelicals to spend decades demanding politicians live chaste and virtuous lives but then vote en masse for a thrice-married, twice-divorced adulterer and former casino owner who was caught on tape bragging about sexual assault?

How can evangelicals justify accusing Barack Obama, a practising Christian who sang hymns in church, of being a secret Muslim while lavishing praise on his successor, who once admitted to never having asked God for forgiveness for anything?

Remember: Trump once claimed the Bible was his favourite book – but couldn’t name any verses from it. He even referred to the Holy Communion as a time “when I drink my little wine and have my little cracker.” So why, then, did evangelicals pull the lever for Trump and why, crucially, do they continue to back him today?

First, don’t discount their opportunism. Ahead of Trump’s inauguration, Franklin Graham was refreshingly blunt: “It’s not about her emails. It’s not about his bad language. It’s about the Supreme Court… and who do you trust to appoint judges that are going to be in favour of Christian liberty?” Trump has not only appointed Neil Gorsuch, an ultra-conservative, pro-life Episcopalian judge, to the Supreme Court but also signed an executive order reinstating the so-called Mexico City Policy, which bars federal funds from going to international NGOs that perform or “promote” abortions. The former pro-choice donor to the Democratic Party is now giving conservative evangelicals exactly what they want.

Second, don’t discount their partisanship. The vast majority of evangelicals have long identified as Republicans and the vast majority of Republicans voted for Trump on party lines. Polarisation in the United States is at an all-time high and party affiliation was one of the best predictors of support for Trump in 2016.

Third, don’t discount the race factor. Only 35 per cent of non-white evangelicals voted for Trump compared to 59 per cent of non-white evangelicals who voted for Clinton. Jim Wallis, a progressive evangelical pastor and former spiritual adviser to Barack Obama, told me earlier this year that “black evangelicals, Hispanic evangelicals… did not vote for Donald Trump. White evangelicals did… because they were more white than evangelical.”

Despite all this, it would be both unfair to tar all evangelicals with the orange brush of Trumpism. Some, such as Russell Moore, one of America’s most influential evangelicals and a leading figure within the Southern Baptist Convention, have been #NeverTrump from the very beginning.

In a speech ahead of the election, Moore slammed his fellow evangelical leaders who he said had elevated politics above faith and had “waved away some of the most repugnant aspects of immorality” to back their preferred presidential candidate.

“The Religious Right,” Moore warned, “turns out to be the people the Religious Right warned us about.”