GEOFF BENNETT: White evangelical Christians have been among President Trump's most loyal supporters for more than a decade now.

And while our new PBS News/NPR/Marist poll shows that most still approve of the president, there are signs that support may be slipping as the midterms approach.

Here's Stephanie Sy.

STEPHANIE SY: On a Wednesday night at Village Church in Blythewood, South Carolina, Pastor Erik Estep is preaching from his pre-midterm election sermon, the Bible and politics.

PASTOR ERIK ESTEP, Village Church: I believe the church is the bulwark of truth for our nation.

And it will take people like you and churches like this church to protect this nation spiritually and morally.

STEPHANIE SY: White evangelical Christians have been the bedrock of Donald Trump's support for more than a decade, and they largely still are.

In the latest PBS News/NPR/Marist poll, 66 percent say they approve of the job Trump is doing as president, 26 points higher than the number of Americans overall who say the same.

As Trump rallies his base ahead of the midterm elections, nearly three-quarters of white evangelicals also plan to back Republicans for Congress.

For Trump, it's a bond that once seemed unlikely.

In 2016, candidate Trump rocketed to the top of the Republican primary, a thrice-married New York real estate mogul caught on tape bragging about groping women and accused of relationships with more than one porn star.

DONALD TRUMP, President of the United States: I stand before you today to fulfill one of my highest and most important duties under the United States Constitution, the nomination of a Supreme Court justice.

STEPHANIE SY: But, as president, he accomplished what has long driven many Christians at the polls, his appointment of three conservative Supreme Court justices, which led to the historic overturning of Roe v. Wade and a rollback of abortion protections for millions of American women.

Estep acknowledges his congregants don't all vote alike, but making abortion illegal is one issue where they are mostly aligned.

PASTOR ERIK ESTEP: To vote according to what our faith prescribes us to vote.

Some people have different perspectives, but there's not much of a different perspective when it comes to issues of abortion and life.

I think the Bible's pretty clear.

STEPHANIE SY: But even among evangelicals, Trump's support has slipped, reflecting an overall fraying of his coalition.

His approval rating among those that voted for him has dropped 12 points since the start of his second term.

That falloff is particularly steep among Latinos and young voters in other recent polling.

Even at Village Church in South Carolina, some are wavering.

CYNTHIA CARROLL, South Carolina Voter: I was a Republican.

I voted Donald Trump into -- as president.

And now I'm more on the fence between conservative and a Democrat.

STEPHANIE SY: Until recently, that loyalty had survived some striking moments, like when conservative Charlie Kirk was assassinated last year and his widow, Erika, chose to forgive his killer.

ERIKA KIRK, CEO, Turning Point USA: I forgive him because it was what Christ did and is what Charlie would do.

STEPHANIE SY: President Trump took a different stance.

DONALD TRUMP: That's where I disagreed with Charlie.

I hate my opponent.

STEPHANIE SY: And this spring, the president posted an AI image of himself appearing as a Christ-like healer.

DONALD TRUMP: I did post it.

STEPHANIE SY: After Christian leaders labeled it blasphemous, Trump deleted it, explaining he thought the image portrayed him as a doctor, which he also is not.

ROBERT JONES, CEO, Public Religion Research Institute: I think part of it is really about a vision of the country that he has promised them.

STEPHANIE SY: Robert Jones, president of the Public Religion Research Institute, says the evangelical support Trump does still enjoy is rooted in a certain vision of America.

ROBERT JONES: The message is, we're a white Christian country.

We're losing that identity.

But if you stick with me, I'm going to make sure that we keep that identity.

STEPHANIE SY: But voters who identify as Christian may have more options this election.

Christian faith leaders are running for the Senate as Democrats in Kansas and Texas.

In reliably red South Carolina, where the Senate race is unusually tight.

Republicans are trying to energize evangelical support for Darline Graham by focusing on transgender issues.

DONALD TRUMP: The Democrat who Darline is running to defeat is a far left political hack who supports transgender for everybody and believes in telling confused children they're trapped in the wrong body.

STEPHANIE SY: During a recent campaign rally in the state, Trump painted Democrats as enemies of conservative values.

ROBERT JONES: So when you have, like, that willingness to like literally demonize your political opponents, and then you have got a group that has been attached to you by party and religion, it sets up a kind of toxic environment.

STEPHANIE SY: For his part, Pastor Erik Estep does not endorse specific candidates or a party in his sermon.

PASTOR ERIK ESTEP: We think that it falls on pastors.

If you want people to respond and to get out and to be to be heard, well, there has to be some sort of motivation.

STEPHANIE SY: What motivates his congregants this year may well be critical on Election Day.

For the "PBS News Hour," I'm Stephanie Sy.