Former Rep. Beto O’Rourke said Thursday that churches and other religious institutions that oppose same-sex marriage should lose their tax-exempt status, taking the Democratic presidential debate into uncharted — and controversial — territory.

The Texas Democrat was asked about the concept by CNN anchor Don Lemon at a 2020 candidates' forum on LGBTQ issues co-hosted by the network and Human Rights Campaign Foundation.

“Do you think religious institutions like colleges, churches, charities should they lose their tax-exempt status if they oppose same-sex marriage?” Lemon asked.

“Yes,” O’Rourke replied. “There can be no reward, no benefit, no tax break for anyone, or any institution, any organization in America, that denies the full human rights and the full civil rights of every single one of us. And so as president, we are going to make that a priority, and we are going to stop those who are infringing upon the human rights of our fellow Americans.”

O’Rourke appeared to go dramatically further than the existing political and legal conversation over LGBTQ rights and religious discrimination, which has largely centered on questions of whether private businesses can decline services to customers or refuse to hire or maintain employees on the basis of sexual orientation or transgender status. Other recent cases have been concerned with the basis on which religious schools can hire or fire staff.

The comments drew applause at the event, but quickly circulated among conservative commentators and drew condemnation from activists that have defended religious institutions in related legal fights.

“Beto O’Rourke’s threat is a direct affront to the constitutional guarantee of religious liberty,” Kelly Shackelford, president of First Liberty Institute, said in a statement.

In another statement, Republican Sen. Ben Sasse of Nebraska called O'Rourke's remarks "bigoted nonsense" that "would target a lot of sincere Christians, Jews, and Muslims."

"This extreme intolerance is un-American," Sasse added.

O'Rourke on Saturday defended his comments hours after President Donald Trump referred to him as a "wacko" over the proposal.

"This from a man who’s used his office to stoke hate, fear, and discrimination. Who tried to ban Muslims," O'Rourke said in a tweet. "Anyone can believe what they want —but organizations that discriminate when they provide public services should not be tax-exempt.

In an e-mail, O'Rourke spokeswoman Aleigha Cavalier suggested the candidate had been misinterpreted, but did not elaborate on his position in detail.

“Of course, Beto was referring to religious institutions who take discriminatory action," she said. "The extreme right is distorting this for their own agenda.”

Cavalier added that O'Rourke defined discriminatory action as "denying public accommodation" on the basis of gender, sexuality, or marriage.

A Human Rights Campaign Foundation spokesman said the group does not have a formal position on the issue O'Rourke raised.

It’s unlikely that efforts to end tax-exempt status for many religious organizations on the basis of opposition to same-sex marriage would pass legal muster given recent precedent upholding a variety of constitutional protections for churches, clergy and religious rituals.

Writing the Supreme Court majority opinion legalizing gay marriage, Justice Anthony Kennedy emphasized that “religions, and those who adhere to religious doctrines, may continue to advocate with utmost, sincere conviction that, by divine precepts, same-sex marriage should not be condoned.”

Marcia McCormick, a professor at St. Louis University School of Law, said there are some legal distinctions between belief and actions and between religiously affiliated institutions like colleges, which courts have ruled cannot discriminate on the basis of race, and churches, which have broader rights.

"There is kind of a continuum," she said. "Religious beliefs alone about religion are the most protected, secular kinds of actions are least protected."

Michael Wear, who led faith outreach efforts for President Barack Obama’s re-election campaign, warned that O’Rourke was risking alienating religious voters across the ideological and denominational spectrum.

“If that isn’t a religious freedom violation, I don’t know what is,” he said. “It’s so facially unconstitutional that it’s hard for people to believe there isn’t ill will involved in even suggesting it.”

While O’Rourke stood out in last night's forum, Wear said he was concerned that Democrats at the event more broadly failed to acknowledge and address concerns religious voters might have about how new anti-discrimination measures might affect their communities.

“So many of these candidates are running saying they’ll be president of all Americans," he said. "They’re going to have to reconcile that with how they approached some of these issues last night."