WATCH: Flailing Ben Sasse defends ‘rude and undisciplined’ Trump nominee while promoting new book on civility

MSNBC's Mika Brzezinski challenged Sen. Ben Sasse (R-NE) to justify his vote to confirm Brett Kavanaugh to the Supreme Court after calling out partisan tribalism.

The "Morning Joe" co-host pointed to Kavanaugh's testimony during a hearing with sexual assault accuser Christine Blasey Ford, saying the judicial nominee issued a partisan rant that she believes should have disqualified him.

"I want to follow up and try to understand your vote more," Brzezinski said. "Because he even said in 2015 in a speech about what it means to be a judge, to be on the bench, and he described the attributes of that person -- and then he went through every stop sign of his own description of what it means to be a judge."

"He was rude," she added. "He was defiant. He showed he was political, and he was very undisciplined during his opening statements by his own definition of what it means to be fit to be a judge. So while I'm not saying those behaviors made him guilty, but I am asking you why they didn't make him unfit?"

Sasse, who's promoting a new book on civility, seemed thrown for a loop by Brzezinski's challenge.

"Mika, it's an important question," he began. "I think we're 32 years into the decline of the Senate confirmation process, going back to (Robert) Bork in 1986 and coming forward. We have a trend line that looks like crap, and it's headed to a bad place. We can do Hatfields and McCoys from here on out."

Sasse insisted that he and other senators carefully deliberated Kavanaugh's nomination, and he justified the nominee's partisan screed during a Senate Judiciary Committee hearing by blaming the accusers and their attorneys.

"I think people like Michael Avenatti were doing something different," Sasse said. "When you get accused of being involved in gang rape and your daughters are hearing all that stuff from their friends, it's understandable that somebody would be outraged."

Sasse admits the confirmation process was a debacle, but he excused Kavanaugh's behavior during the hearings and outside the Capitol.

"I wish the hearing had gone quite differently than it did, and there's lots of blame to go around on why the hearing did go the way did it," Sasse said. "It's very unorthodox that now-Justice Kavanaugh wrote the op-ed he did after that where he partially repented for the way he presented himself in that hearing, the Wall Street Journal op-ed that came out about a week later, where he said there should be no aisle at the Supreme Court, no caucus rooms at the Supreme Court."

"I think we all know we're headed towards an ugly red and blue jersey place in the judiciary, and that's a bad 32-year trend line," he added. "One guy who has been accused of gang rape and speaking about that and losing his cool, I don't think is disqualifying, but I think it was unfortunate, and I think Justice Kavanaugh agrees it was unfortunate."