Throughout his first term, one group of Americans who have been reliably in President Donald Trump's corner are white Christians, particularly white evangelicals, who remain a solid base for the Republican candidate.

In 2016, an overwhelming 81 percent of white evangelicals voted for Trump, making the group the president's best chance at re-election. An estimated 25 percent of U.S. Christians identify as evangelical protestants, and among them 76 percent are white.

Trump has pursued policies that have convinced religious Americans who feel alienated from the more liberal and multicultural cities that the thrice-married businessman, who rarely goes to church, is their guy. To have a leader championing their causes, from anti-abortion advocacy and religious freedom to support for Israel, proves much more important to these voters than any discomforts they might have with the president's style and rhetoric.

Trump has repeatedly told conservative Christians that their way of life is under siege and promised to restore the U.S. to a Christian country guided by Judeo-Christian values.

'Christianity will have power'

At the core of this vision is the belief that America is a Christian nation, with a set of narratives and conservative values governing politics and civic life, according to scholars Andrew Whitehead and Samuel Perry, who found that a significant number of Americans view their country this way.

"Christianity will have power," Trump famously remarked on the 2016 campaign trail. From there, he stepped into the role of defending the country from perceived threats from secular progressivism.

This is a role so frequently brought up to the point of coming off as transactional. At a recent rally in Wisconsin, Trump explicitly stated that the historic move by his administration to recognize Jerusalem as the capital of Israel was done "for the evangelicals" who, in Trump's own words, are more excited about it than Jewish people.

Then at the Republican National Convention, the presidential nominee addressed those same Americans directly. "This election will decide whether we will defend the American way of life, or whether we allow a radical movement to completely dismantle and destroy it," he said.

The administration's anti-abortion efforts are a major part of the glue keeping Trump's base together. The appointments of conservative pro-life judges on the Supreme Court and in federal courts, defunding abortion provider Planned Parenthood and the prospect of overturning Roe v. Wade won hearts from the conservative community at large.

Some experts believe there is also an element of nationalism to Trump's appeal which is centered around whiteness, patriarchy and heteronormativity – a socialized assumption about who belong in the U.S. and who do not. Writing about what they have termed "Christian nationalism," Whitehead and Perry argued that the rise of Trump "is as ethnic and political as it is religious."

It is perhaps more telling when considering the voting habits of non-white Christians, who share similar views on issues like abortion and gay marriage with their white counterparts. Contrary to popular belief that U.S. Christians typically vote Republican, non-white Christians, especially black Protestants, have overwhelmingly backed Democrats in past elections and are expected to do so this year.

However, white Christians have consistently favored Republican candidates in elections since 2008, Pew Research data shows. The voting habits of white Catholics and white mainline Protestants have mostly remained unchanged in recent elections, though their partisan preferences are more evenly split than that of white evangelicals, with respectively 59 percent and 58 percent supporting Trump in 2016.

What's changed now?

Amid the uncertainty of the COVID-19 pandemic and widespread social unrest over racial justice, recent polling indicated that support for Trump among faith groups is slipping. The reason for this is the president's perceived lack of Christian virtues, especially kindness, compared to his Democratic challenger Joe Biden, according to Vote Common Good, which conducted the "Vice and Virtue" survey in five swing states in August.

Doug Pagitt, a white evangelical pastor and executive director of Vote Common Good, believes the current environment in the U.S. – with over 200,000 COVID-19 deaths and a nationwide reckoning about racism – will weaken Trump's standing among religious Americans.

Biden, on the other hand, may be better positioned among white Catholics due to his own Catholic background as well as his regular church attendance. Meanwhile, polling data from September suggests Biden has as high as 30 percent of white evangelical support, a significant increase from the 19 percent for Clinton in 2016.

"People of faith who didn't vote for Hillary Clinton saw her as more corrupt and less kind than Donald Trump, and now some of those same voters see Donald Trump as more corrupt and less kind than Biden," Pagitt said.

In the Biden campaign's outreach to faith communities, the Democrats have framed "the real religious issue" at stake as systemic racism, appealing to Christians' moral imperative to care for the weak. However, one big road block for Biden is his stance on abortion after the Democratic candidate withdrew his support for a ban on federal-funded abortion procedures. His running mate Kamala Harris is also known to be pro-choice.

But Trump obviously has more to worry about this November. The Public Religion Research Institute shows white Christian support for the president dropped from 54 percent in 2019 to 47 percent in July. Calling out the president's "unchristian" ways in a joint op-ed in TIME, Pagitt and black Baptist minister Al Sharpton urge U.S. Christians to treat the election as "a test of faith."

"This is a different election for several reasons, but one of them is that the sheer disgust most religious voters felt for Hillary Clinton in 2016 doesn't exist with Joe Biden," said one adviser to the Trump campaign as quoted by Politico.

"If President Trump wants to ensure those voters still view him as the best choice, he needs to show he's not just a champion of their causes but a believer in the cause himself."