As Republicans struggle to craft a sweeping tax package — a process already rife with political land mines — they are preparing to add another volatile element to the mix: a provision that would end a six-decade-old ban on churches and other tax-exempt organizations supporting political candidates.

The repeal of the “Johnson Amendment” is being written into tax legislation developed in the House of Representatives, according to aides. President Trump has vowed to “totally destroy” the provision at the behest of evangelical Christians who helped elect him.

The inclusion of the repeal in broader tax legislation could bolster its chances. A stand-alone bill would almost certainly face a filibuster in the Senate, where opponents fear the measure would effectively turn churches into super PACs.

But the prospects for comprehensive tax reform also remain far from certain given differences in priorities among House and Senate Republicans and an array of business groups prepared to fight provisions that would hurt them.

Ways and Means Committee Chairman Kevin Brady (R-Tex.) backs allowing churches and other tax-exempt groups to support political candidates. (Joshua Roberts/Reuters)

It is also unclear whether Trump, who has struggled to navigate Capitol Hill, supports the strategy of including the repeal in a broader tax bill, which is likely to include corporate and middle-class tax cuts.

“Republicans are going to have enough problems getting tax reform done,” said Jim Manley, a longtime aide to former Senate minority leader Harry M. Reid (D-Nev.). “If they start loading it up with unrelated stuff like this one to score political points, it will just get bogged down and go nowhere.”

The measure at issue is named for Lyndon B. Johnson, who introduced it in the Senate in 1954, nine years before he became president. The provision prohibits tax-exempt organizations, including houses of worship, from endorsing or opposing political candidates.

Repeal of the amendment has been sought primarily by conservative Christian leaders, who argue that it is used selectively to keep them from speaking out freely in church.

During the campaign, Trump spoke out in favor of ending the prohibition, and he strongly reiterated his support during the National Prayer Breakfast shortly after taking office.

White House spokeswoman Natalie Strom said Trump still supports repeal, but she would not comment on whether he backs the approach advocated by Rep. Kevin Brady (R-Tex.), chairman of the House Ways and Means Committee.

Ralph Reed, chairman of the Faith and Freedom Coalition, which counts repeal of the Johnson amendment as a top priority, said he is not as concerned with how the repeal happens as he is that Trump and other Republican leaders keep their promise.

Sen. Ron Wyden (D-Ore.) opposes moves to lift restrictions on tax-exempt groups backing political candidates. (Jahi Chikwendiu/Washington Post)

“That would be fine with us, if it were to become law as part of a tax package,” Reed said. “We’d like to have an up-or-down vote, but this might make it easier to pass.”

Houses of worship make up just a fraction of the universe of 501(c)(3) organizations, named for a portion of the tax code.

Last week, nearly 4,500 such organizations signed onto a letter to congressional leaders, urging them not to weaken or repeal the amendment. It also argued that allowing nonprofit organizations to support candidates would create a loophole in campaign disclosure laws because contributions to many such groups are not made public and are tax deductible.

“Nonpartisanship is a cornerstone principle that has strengthened the public’s trust of the charitable community,” the letter said.

Fred Wertheimer, president of Democracy 21, one of the groups that signed the letter, criticized any attempt by House leaders to attach repeal of the Johnson amendment to broader tax legislation.

“It’s simply an effort to ram it through without getting a vote on it,” Wertheimer said.

The aim of repealing the Johnson amendment is also not universally embraced by all religious groups. A coalition of 99 organizations, including many Jewish and Baptist groups, sent a separate letter to Congress last week, urging that the ban stay in place.

In a statement Thursday, Sen. Ron Wyden (Ore.), the ranking Democrat on the Senate Finance Committee, spoke out against efforts to eliminate the Johnson amendment.

“A repeal would undermine the sanctity of our religious institutions, increase the flow of dark money in politics and force taxpayers to foot the bill for special interests,” Wyden said.

But Jerry Falwell Jr., an evangelical Christian leader and president of Liberty University, said that such concerns are overblown, saying a repeal could be “carefully crafted” to ensure that churches and other tax-exempt organizations are permitted to spend only a small percentage of their funds on support of candidates.

“That just needs to be worked out,” he said.

Falwell said religious leaders are mostly concerned about the ability to speak freely and not risk losing their institution’s tax-exempt status with the Internal Revenue Service. Most are not interested in turning their churches into super PACs, he said.

Under current law, churches are free to engage in political activity; the restrictions under the Johnson Amendment are triggered by their acceptance of tax-exempt status.

As a candidate, Trump voiced his opposition to the Johnson Amendment during a speech in June to a group of hundreds of conservative Christian faith leaders who met with him in New York. He also pressed the issue in smaller settings, including in a meeting with faith leaders before a rally in North Carolina shortly before the election, said Tami Fitzgerald, executive director of the NC Values Coalition, who was one of the participants.

And during his appearance at the National Prayer Breakfast in February, Trump vowed to “get rid of and totally destroy the Johnson amendment and allow our representatives of faith to speak freely and without fear of retribution.”