A politician typically goes on a late-night comedy show so that he can deliver his message to a wide audience, banter with a friendly host, and generally prove to the world that he is, as Hillary Clinton might put it, “a real person.”

When Ted Cruz walked off stage after his appearance with Stephen Colbert on Monday night, he had accomplished none of those goals.

Colbert greeted his frequent conservative foil politely enough, but he then proceeded to give him the toughest interview of his brief tenure on CBS. Interrupting Cruz repeatedly, Colbert confronted him over his opposition to gay marriage, his selective adulation of Ronald Reagan, and his uncompromising political style. By the end of the appearance, the host had to step in to stop his studio audience from jeering the Republican presidential hopeful. “Now guys, guys, however you feel, he’s my guest, so please don’t boo him,” Colbert pleaded as Cruz began to give a boilerplate response on gay marriage. The crowd quieted.

The tension in the Cruz interview came during the second segment, when Colbert laid a bit of a trap for him by asking how the modern Republican Party could hold Reagan in such high esteem given that he raised taxes and signed legislation granting amnesty to undocumented immigrants. “Neither of those things would allow Ronald Reagan to be nominated today,” Colbert said. “So how can you truly emulate Ronald Reagan?” Noting—as Democrats frequently do—that Reagan repeatedly struck agreements with House Speaker Tip O’Neill, Colbert asked whether that’s what voters wanted—a president who would work across the aisle, delivering “action” rather than simply “principles.”

Cruz quickly launched into a defense of his reputation as a political fighter, saying he meets few voters who want more compromise with President Obama. And often on late-night shows, that would be enough. But Colbert cut him off twice, forcing him to say whether he supported Reagan’s tax increases and amnesty program. “No, of course not,” Cruz finally replied.

A few minutes later, Cruz had succeeded in turning the conversation back to his core campaign message—well, almost. “What I’m fighting for are simple principles,” he began. “Live within our means. Stop bankrupting our kids and grandkids. Follow the Constitution.”

“And no gay marriage,” Colbert added.

Uh oh.

And no gay marriage,” Colbert repeated, as a way of showing he did not mean the interruption as a throw-away laugh line.

Cruz began to give his standard talking points on why he opposed the Supreme Court’s decision earlier this year. But he slipped up, and Colbert caught it. “Under the Constitution, marriage is a question for the states,” Cruz said.

“Marriage isn’t mentioned in the Constitution,” Colbert corrected him, to the crowd’s delight. Cruz quickly clarified himself, arguing that marriage should be governed not by the 14th amendment’s guarantee of equal rights and due process but by the 10th amendment, which says that any powers not given to the federal government are reserved for the states and the rights. Therefore, marriage should be a question for the states.

It was a decent recovery, but Cruz had lost the audience. Colbert’s exhortation not to boo kept them in line, and he ended the interview a minute later.

Cruz deserves credit for making the appearance. He’s a Republican who often seeks out safer audiences, whether on Fox or conservative talk radio. And it’s no longer a secret that Colbert is a much more challenging interviewer in his new show than any of his late-night colleagues. Donald Trump and Hillary Clinton each had far easier appearances with Jimmy Fallon last week. (Trump goes on Colbert’s show on Tuesday.) Carly Fiorina appeared on The Tonight Show opposite Cruz on Monday, and while Fallon did get her to respond to Ben Carson’s comments on Muslims and the presidency, it was a much lighter affair.

Yet even by Colbert’s standards, his interview with Cruz featured much tougher treatment than any of his other political interviews to date. When he hosted Jeb Bush on his debut show, he mixed in some serious queries with a number of gags. Colbert steered almost completely clear of politics in his moving interview with Biden. And when Bernie Sanders appeared on the show last week, Colbert gave him space to deliver his campaign talking points with little interruption.

Indeed, Colbert seems to be developing a habit of revealing his attitude toward a politician in the different ways he shows them off his stage. Concluding his interview with Bush, he told him, by way of a compliment, that he might possibly vote for him. Colbert said goodbye to Biden by practically pleading with him to run for president. With Cruz, there were no deadpan, and no praise. “I really appreciated you sharing your views with us,” Colbert said, “and good luck with the campaign.”