BILLINGS, Mont. — Montana tribal leaders have urged Republican U.S. Senate candidate Tim Sheehy to apologize for remarks he made to supporters that Native Americans were “drunk at 8 a.m.” and throwing beer cans at him on the Crow reservation.

Audio recordings of Sheehy’s derogatory comments were obtained and published by Char-Koosta News, the official publication of the Flathead Indian Reservation.

Sheehy is endorsed by former President Donald Trump as he challenges three-term Democratic incumbent Sen. Jon Tester in one of the most closely watched Senate races in the country.

A Republican victory could help flip control of a closely divided Senate.

In one of the recordings, Sheehy is heard saying that his ranching partner is a member of the Crow tribe with whom Sheehy ropes and brands cattle on the tribe’s reservation in southeastern Montana.

“It’s a great way to bond with all the Indians, to be there while they’re drunk at 8 a.m.,” Sheehy said.

In another recording, he describes a horseback ride during the Crow Fair parade, an annual Crow Agency gathering that includes powwows, a rodeo and other events.

“If you know a tough crowd, you have to go to Crow Res,” Sheehy says. “They let you know if they like you or not: There are Coors Light cans flying by your head.”

The Rocky Mountain Tribal Leaders Council, which represents 11 tribes and First Nations in the western United States and Canada, said Sheehy’s comments perpetuated stereotypes about Native Americans.

Council Chairman Bryce Kirk asked Sheehy to apologize in a letter to the campaign obtained by The Associated Press on Tuesday.

“You ask for our votes and then go to your fundraiser, ironically with free flowing alcohol and laughter at our expense behind closed doors, and insult us with a stereotype that only seeks to gravely diminish and dishonor our people,” Kirk wrote. “Crow people are not your slogan. Native Americans are not your slogan.”

It’s unclear whether Sheehy’s comments will still be fresh in voters’ minds when they start casting ballots. But political analyst Paul Pope said their “inappropriate” nature could encourage more Native Americans to register to vote, which could strengthen Tester.

“Maybe there are some undecided people and this could be a tipping point for them,” added Pope, a professor at Montana State University in Billings.

A spokesman for Sheehy’s campaign did not dispute the authenticity of the recordings, which the tribal newspaper said came from fundraising events in Montana last November.

Sheehy is a former Navy SEAL with no political experience who moved to Montana a decade ago and founded an aerial firefighting company. He knows members of the Crow tribe and travels to the reservation to work with them on cattle ranching, spokesman Jack O’Brien said.

“He works with them, he helps them with their branding,” O’Brien said. “What people are implying about him is not really a reflection of who he is.”

He did not say whether Sheehy would apologize or otherwise respond to the tribal leaders’ request.

Montana has seven Indian reservations and nearly 70,000 Native Americans, or about 7 percent of its total population, according to U.S. Census data. The voting bloc has long been considered Democratic-leaning, but Montana Republicans have courted tribal leaders in recent years in hopes of winning their support in elections.

Crow Tribe Chairman Frank White Clay did not immediately respond to a message left at his office seeking comment.

Tester’s campaign declined to comment on the matter.

Last month, White Clay and other Crow representatives attended a rally in Bozeman, with Trump and Sheehy in attendance. White Clay told an AP reporter that their presence was not meant as an endorsement. He said the tribe wanted to maintain good relations with whichever administration takes office.

Char-Koosta News Editor Sam Sandoval said Sheehy’s campaign has not responded to his outlet’s questions about the recordings, which he said came from a credible source who wanted the comments published in a tribal newspaper.

“For a lot of tribal members, hearing this statement that they’re drunk at 8 a.m. really hits a nerve that Native people have been working to change for years,” Sandoval said.