As one of the most vulnerable Democrats up for re-election and a potential swing vote in Supreme Court nominee Brett Kavanaugh’s confirmation process, Heidi Heitkamp, senator from North Dakota, knew her constituents would be closely scrutinizing her vote.

Heitkamp, who’d voted “yes” on President Donald Trump’s first Supreme Court pick Neil Gorsuch, said she’d initially planned on approving Kavanaugh’s nomination. But said she ultimately changed her mind after watching Kavanaugh’s testimony ― with the sound off.

“It’s something I do,” Heitkamp told CNN on Monday of soundless observation. “We communicate not only with words, but with our body language and demeanor.”

“I saw somebody who was very angry, who was very nervous, and I saw rage that a lot of people said, ‘well of course you’re going to see rage he’s being falsely accused,’ but it is at all times you’re to acquit yourself with a demeanor that’s becoming of the court,” Heitkamp continued.

The senator said the final straw came when Kavanaugh snapped at her colleague, Sen. Amy Klobuchar (D-Minn.), who’d asked him if he’d ever blacked out from drinking.

“Have you?” the judge retorted.

Kavanaugh — who was confirmed to the court on Saturday by a 50-48 Senate vote, mostly along party lines — later apologized to the senator.

North Dakota Sen. Heidi Heitkamp was ready to vote "yes" on Supreme Court Justice Brett Kavanaugh. Then she watched him with the sound off. https://t.co/lcgBGP7dqH pic.twitter.com/ThLGACVZSO — CNN Politics (@CNNPolitics) October 9, 2018

In an interview with “60 Minutes” that aired Sunday, Heitkamp said she had been disturbed by the level of “combativeness” she’d witnessed from Kavanaugh.

“When he got into the answering questions and the back and forth, I thought, ‘That’s not someone I want sitting on the bench,’” she said.

Heitkamp also criticized Trump for publicly attacking Christine Blasey Ford, one of at least three women who accused Kavanaugh of sexual misconduct.

“It made me sad because I didn’t think it was what we would want a president of the United States to do,” she said.

Heitkamp’s Kavanaugh vote could leave the senator, who is currently trailing in the polls in North Dakota (a state that Trump won by 36 points), even more vulnerable in the midterms.

But the senator stressed at a Sunday Oktoberfest event in Wyndmere, North Dakota, that her vote had been based on what was “right” and not political calculus.

“The political rhetoric is you can’t vote that way if you expect to come back. I tell people Ray and Doreen Heitkamp didn’t raise me to vote a certain way so that I could win. They raised me to vote the right way,” she said, referring to her parents.

CNN noted that Heitkamp received a standing ovation from the event’s attendees.

Yesterday, I was on @60Minutes to explain why I voted against Judge Kavanaugh to serve on the US Supreme Court. My decision wasn't about politics—it was about using my own judgment & doing the right thing. Watch there: https://t.co/AJpF6nLq6Z — Sen. Heidi Heitkamp (@SenatorHeitkamp) October 9, 2018