Mayor Pete Buttigieg, who this week formally announced his candidacy for the Democratic presidential nomination, has caused a stir by criticizing the religiosity of President Trump and Vice President Pence, his hoped-for General Election opponents. On Wednesday, Buttigieg backed off calling them Pharisees, after some Jewish protest that this New Testament term for priestly hypocrites refers to the rabbinic precursors of contemporary Judaism.

But there’s something unprecedented about his criticism that should not be overlooked.

Let’s pick up the story on April 3, when USA Today columnist Kirsten Powers reported asking Buttigieg if he thinks Trump is a Christian. His response:

I’m reluctant to comment on another person’s faith, but I would say it is hard to look at this president’s actions and believe that they’re the actions of somebody who believes in God. I just don’t understand how you can be as worshipful of your own self as he is and be prepared to humble yourself before God. I’ve never seen him humble himself before anyone. And the exaltation of yourself, especially a self that’s about wealth and power, could not be more at odds with at least my understanding of the teachings of the Christian faith.

Quoting from this statement on Meet the Press April 7, Chuck Todd asked Buttigieg about evangelical support for the president. “Well, it’s something that really frustrates me because the hypocrisy is unbelievable,” replied the mayor.

Here, you have somebody who not only acts in a way that is not consistent with anything that I hear in scripture or in church, where it’s about lifting up the least among us and taking care of strangers, which is another word for immigrants. And making sure that you’re focusing your effort on the poor. But also personally, how you’re supposed to conduct yourself. Not chest thumping look-at-me-ism, but humbling yourself before others. Foot washing is one of the central images in the New Testament. And we see the diametric opposite of that in this presidency. I think there was perhaps a cynical process where he decided to, for example, begin to pretend to be pro-life and govern accordingly. Which was good enough to bring many Evangelicals over to his side. But even on the version of Christianity that you hear from the religious right, which is about sexual ethics, I can’t believe that somebody who was caught writing hush money checks to adult film actresses is somebody they should be lifting up as the kind of person you want to be leading this nation.

The following day, Buttigieg, a gay Episcopalian, had this to say about his marriage in a speech at the LGBTQ Victory Fund National Champagne Brunch:

My marriage to Chasten has made me a better man. And yes, Mr. Vice President, it has moved me closer to God. (applause) You may be religious and you may not. But if you are, and you are also queer, and you have come through another side of a period of wishing that you weren’t, then you know that that message, that this idea that there is something wrong with you, is a message that puts you at war not only with yourself but with your Maker. And, speaking only for myself, I can tell you that if me being gay was a choice, it was a choice that was made far far above my pay grade. And that the thing I wish the Mike Pences of the world would understand: that if you have a problem with who I am, your problem is not with me. Your quarrel, sir, is with my Creator.

In an interview on CNBC April 10, Pence picked up the gauntlet: “He’s said some things that are critical of my Christian faith and about me personally. And he knows better. He knows me.”

“I’m not critical of his faith; I’m critical of bad policies,” Buttigieg replied during a taping of the Ellen DeGeneres show April 11. “I don’t have a problem with religion. I’m religious, too. I have a problem with religion being used as a justification to harm people and especially in the LGBTQ community.” Claiming that he was “not interested in feuding with the vice president,” he added, “But if he wanted to clear this up, he could come out today and say he’s changed his mind, that it shouldn’t be legal to discriminate against anybody in this country for who they are. That’s all.”

Religious contention of this sort is not unheard of in the history of American presidential campaigns. What’s unprecedented is for candidates to engage in it.

Like Trump, Thomas Jefferson was attacked as an atheist for supporting the French Revolution, and for immorality in the matter of Sally Hemings. But the attacks came from the Federalist press, not from his presidential rivals, John Adams in 1796 and 1800 and Charles Pinckney in 1804. (Let it be noted that, also like Trump, Jefferson enjoyed widespread evangelical support.)

Abraham Lincoln, who never joined a church, was widely thought to be an unbeliever or, at most, a Deist. But the only political opponent who publicly assailed him for this was the evangelist Peter Cartwright, whom he ran against for Congress in 1846.

The 1884 election is famous for the charge that the Democratic standard bearer, Grover Cleveland, represented the party of “Rome, Romanism and Rebellion.” But it was a Presbyterian minister who made the charge, not Republican candidate James G. Blaine. Cleveland, himself a Presbyterian, was likewise dogged by charges of immorality for having fathered a child out of wedlock, but again, not out of Blaine’s mouth.

In 1928 and 1960, Democratic presidential candidates Al Smith and John F. Kennedy were subject to attacks because they were Catholics. But as the nicknames for the attacks (“The Whispering Campaign” and “The Underground Campaign” respectively) indicate, these did not issue from GOP candidates Herbert Hoover and Richard Nixon themselves.

So why has Buttigieg gone where no presidential candidate has gone before?

In part, it seems, Trump’s own readiness to indulge in personal religious invective (e.g. Ilhan Omar) has erased the norm that principals leave these attacks to supporters. But it’s hard to avoid the conclusion that for a progressive Christian like Buttigieg, the president’s hostility to desperate immigrants, his encouragement of white nationalism, and his preferential option for the rich are just too much to bear.

The burden of Buttigieg’s criticism of Trumpian religiosity is familiar enough—that the president doesn’t behave like a Christian together with the corollary charge against white evangelicals for their wholehearted support of him. By contrast, his animus toward Pence looks personal.

It was Pence who as governor of Indiana in 2015 pushed through legislation designed to make it easier for people to withhold services from gays and lesbians on religious grounds. Although the governor was quickly forced to reverse course, the gay mayor of South Bend doubtless harbors some anger towards him about the episode.

And why shouldn’t he? When the law is changed to facilitate discrimination against your kind, you get to criticize it.

But notwithstanding his claim that he is only critical of Pence’s “bad policies,” there’s no question that Buttigieg has also called his faith in question, at least with respect to what he believes about sexuality. Saying, “you have a quarrel, sir, with my Creator,” is about as in-your-face religiously as it gets.

For 40 years, religious conservatives have assailed religious liberals for abandoning religious truths. Those chickens may finally be coming home to roost.