ATLANTA — Republican President Donald Trump’s pledge to scrap limits on church political activity could have sweeping effects that extend beyond his conservative supporters to more liberal congregations, including the black evangelical church that has long been a key component of the Democratic Party’s electoral machinery.

Yet many prominent black religious leaders say they like the law the way it is. And across the spectrum there are questions about whether churches could be pulled into the campaign finance vortex and effectively become “dark money” committees that play partisan politics without disclosing donors.

“This opens up a can of worms that would undermine the church’s moral authority,” said the Rev. Raphael Warnock, senior pastor at Atlanta’s Ebenezer Baptist Church, where civil rights icon the Rev. Martin Luther King Jr. once preached.

In South Carolina, the Rev. Darrell Jackson doubles as a state senator. He allows politicians to attend Bible Way Church services in Columbia, but says he doesn’t even ask his parishioners to vote for him. “That’s crossing a sacred line,” Jackson said.

Trump reignited the issue last week when he used the National Prayer Breakfast to repeat his campaign pledge to “totally destroy” a rarely enforced 1954 law that threatens religious and many other nonprofit entities with loss of their tax-exempt status if they engage in explicit electioneering, such as endorsing candidates or spending money advertising in a ballot initiative campaign.

The president frames the so-called “Johnson amendment,” named for its original sponsor, then-Sen. Lyndon Johnson, as an assault on religious freedom.

The law does not actually prevent churches or their leaders from weighing in on issues of the day.

Republican and Democratic politicians are fixtures in pews during election season. Theologically conservative evangelicals often emphasize opposition to abortion and same-sex marriage and their unyielding support for Israel — all Republican hallmarks. More liberal evangelicals often tout “social justice,” advocating policies that reflect the Democratic Party. Voices of the Roman Catholic and mainline Protestant churches can be found in both camps.

Warnock said faith and politics necessarily mix.

“You can’t advocate for the poor,” he said, “without being political.” But he said there’s a difference between pushing policy and backing candidates.

Indiana University professor Brad Fulton, who studies political activity in the U.S. religious community, cited research that suggests liberal congregations actually have become more politically active in recent years. Conservative evangelical congregations, meanwhile, appear to have become less so in the decades since the Christian Coalition and Moral Majority movement blossomed to the benefit of Republicans. Those conclusions come from the National Congregations Study, an academic project that tracks activities including hosting political speakers, registering voters and distributing issue-based voter guides.

Fulton said that, of course, some black evangelicals want to make explicit endorsements, while some white evangelicals are wary.

But many prominent black pastors note that their movement never worked in an organized way to jettison the Johnson rule when Democrats were in the White House or in charge on Capitol Hill. Most of the loudest voices for repeal are white conservative evangelicals who cast the law as an unconstitutional muzzle.

The Rev. Mark Harris, a Trump supporter and senior pastor of Charlotte First Baptist Church in North Carolina, said a repeal would “lift a cloud of confusion” he says silences too many pastors. Harris endorsed Trump from his pulpit last fall and participates in Pulpit Freedom Sundays, periodic occasions where hundreds of evangelical ministers openly flout Internal Revenue Service regulations for churches.