Political-minded ministers are flouting federal tax law by preaching politics from the pulpit as part of a nationwide movement to defy the Internal Revenue Service.

The IRS has taken virtually no action against the pastors, whose churches risk losing their tax-exempt status over their election messages.

Clergy are free to talk about hot-button issues such as abortion and gay marriage in front of their congregations, but current law bars tax-exempt religious organizations from endorsing or opposing individuals who run for office.

Lyndon Johnson proposed the rule as a U.S. senator in 1954, and Congress passed the measure that same year. According to the Alliance Defending Freedom, which started the defiance movement, Johnson wanted to stifle nonprofit groups that were backing his opponent.

Critics say the law violates free-speech rights, and church leaders who oppose it have made no secret of their actions on the pulpit, even sending tapes of their political sermons to the IRS.

The defiance movement, known as Pulpit Freedom Sunday, has grown from a few dozen ministers to more than 1,600 over the past six years, according to the alliance.

Church leaders involved in the effort have weighed in on key races that could tip the balance of power in the Senate during this year’s midterms, openly endorsing candidates such Senate Minority Leader Mitch McConnell (R-Ky.) over Alison Lundergan Grimes (D) and Thom Tillis (R) over Sen. Kay Hagan (D-N.C.).

But the clergy don’t just support Republicans.

Jim Garlow, senior pastor at Skyline Church in San Diego, has backed Rep. Scott Peters (D-Calif.) over GOP candidate Carl DeMaio, who is gay. Garlow said the Republican challenger would advance a “radical homosexual agenda” if elected, according to Politico.

The IRS did not respond Monday to repeated requests for comment about whether it plans to crack down on the movement. Politico published a report about the issue that day, saying the agency has refused to disclose whether it is taking action.

The IRS’s reluctance to enforce the tax law suggests it has grown timid about dealing with tax-exempt groups, particularly after last year’s revelations that the IRS had targeted nonprofit advocacy groups for deeper review based on their names and policy positions — an effort that affected mostly conservative organizations.

Any high-profile IRS battle with the pastor alliance before this year’s midterm elections could have fueled the Republican narrative that the Obama administration has used IRS and other federal agencies to stifle right-leaning organizations.

IRS Commissioner John Koskinen, who became head of the agency several months after the targeting scandal emerged, said in an October interview with TaxAnalysts.com that the IRS is “continuing to review churches in the way we have in the last several years.” He also revealed that the agency is examining 92 churches for possible violations.

Koskinen added that the mere existence of an IRS process for reviewing churches has led to misperceptions that “somehow we are doing something very different, and we are going to show up either more aggressively or more often, in a different way than we have in the past.”

The pulpit movement aims to eventually overturn the tax law prohibiting churches from electioneering. But critics of the effort are concerned that such a move would open the door for religious organizations to contribute tithings or other collections directly to candidate campaigns.

At least one group opposed to the movement has tried to force the IRS’s hand. In 2012, the Freedom From Religion Foundation sued the agency for overlooking the actions of churches that engaged in election activities while enforcing the law with nonreligious nonprofits.

The group dropped its suit after IRS lawyers revealed that the agency was reviewing churches but reexamining its processes in light of the targeting scandal.