Of the six candidates on Wednesday night’s Democratic debate stage, Sen. Amy Klobuchar (D-MN) and former South Bend Mayor Pete Buttigieg have a great deal in common: they’re both from the Midwest, they’re both moderates, and they both appear to share a deep and abiding distaste for one another.

While the debate showcased plenty of testy exchanges between candidates with serious differences on politics and policy—ideological opposites Sen. Bernie Sanders (I-VT) and former New York Mayor Mike Bloomberg got into it on several occasions—the Minnesota senator and the former Indiana mayor clashed bitterly over relatively minor differences in policy and political records.

When Klobuchar was asked a question about what she would do to help the young, undocumented migrants known as Dreamers, Buttigieg took the opening to point out that she was the Senate Democrat on stage with the highest rates of confirming Trump’s judicial nominees, and that she had voted to confirm Trump’s nominee to lead U.S. Customs and Border Protection.

“Do you know the message that sends” asked Buttigieg, “in as multilingual a state as Nevada to immigrants?”

Klobuchar’s response was witheringly Midwestern in its iciness.

“I wish everyone was as perfect as you, Pete,” she responded. “But let me tell you what it is like to be in the arena.” The senator then went on to defend her record, saying that she had opposed most Trump judges and that she had supported the CBP nominee because of his background as a career official.

Earlier in the night, Klobuchar and Buttigieg also clashed over a moderator question that raised a misstep the senator had made earlier in the week, when she—unlike Buttigieg—could not recall the name of the president of Mexico at a campaign forum. The question sparked a row about who had greater electoral appeal in the Midwest.

“He’s basically saying that I don’t have the experience to be president of the United States,” claimed Klobuchar. “I am the one, not you, that has won state-wide and congressional district after congressional district. And I will say when you tried in Indiana, Pete, to run, what happened to you? You lost by over 20 points to someone who lost to my friend Joe Donnelly. So don’t tell me about experience.”

In response, Buttigieg cracked a joke at the expense of Minnesota’s favorite son—and Klobuchar’s political mentor. “If winning a race for Senate in Minnesota translated directly to becoming president, I would have grown up under the presidency of Walter Mondale,” he said. “This is different.”

This is hardly the first chapter in the Klobuchar-Buttigieg feud. The Daily Beast reported in December that Klobuchar’s camp saw strategic upside in going after her fellow Midwesterner, a fellow competitor for the “nice vote.” And The New York Times reported in November that the mere mention of the South Bend mayor in a conversation on the Senate floor made the Minnesota senator “extremely agitated.”

The animus between the two continued through the debate’s closure. When the festivities ended, Klobuchar quickly exited the stage, walking behind Buttigieg without appearing to say a word. She eventually made her way to the MSNBC set off in the spin room, where the feud only continued.

“I think Pete decided he was going to try and go after me. That’s fine. I wish he would have tried to be accurate when he did it,” she told Chris Matthews. “I thought what he did was personal… It was one error and he decided to make it the centerpiece of his attack”