The Republican nominee for Montana’s contested Senate seat, Matt Rosendale, is facing accusations that he improperly coordinated with the National Rifle Association on an ad buy after a leaked audio recording was published Thursday by the Daily Beast.

Rosendale’s campaign and the NRA’s lobbying arm, the Institute for Legislative Action, deny any improper activity. They say that the audio reveals only Rosendale discussing an endorsement in his race against Sen. Jon Tester (D) and not any campaign ads.

The audio recording appears to show Rosendale discussing a conversation he had with Chris Cox, the NRA-ILA’s executive director, regarding the group’s planned involvement in the campaign. The Daily Beast reported that Rosendale made the remarks in July at an event in Washington.

“I fully expect that the U.S. Chamber is going to come in, and I fully expect that the NRA is going to come in. I think both of them will be coming in probably right here in August sometime,” Rosendale says in response to a question from an unidentified person on whether outside groups will be spending on his behalf in the race.

He goes on to suggest that the NRA was swayed by the issue of whether Republicans will be able to maintain a Senate majority that can confirm any of President Trump’s future Supreme Court nominees.

“The Supreme Court confirmations are big. That’s what sent the NRA over the line. . . . Chris Cox told me, he was like, ‘Well, we’re going to be in this race,’ ” Rosendale says on the recording.

Democrats said the comments indicate that Rosendale may have coordinated with the NRA in violation of federal laws prohibiting campaigns from working with interest groups on political advertising.

“This audio raises serious concerns about potential illegal coordination between Matt Rosendale and an outside, dark-money group coming into Montana to support him,” Tester spokesman Chris Meagher said in a statement.

The Montana Democratic Party pointed to a TV ad launched by the NRA in Montana last week as evidence that the group was “in this race” as Rosendale claimed it would be. The ad takes aim at Tester on gun control and his votes to confirm two of President Barack Obama’s Supreme Court nominees.

Rosendale’s campaign confirmed that the audio was of the candidate but argued that it did not show evidence of any discussion of advertising.

“The only thing this audio proves is that Matt sought the endorsement of the NRA — and we’re proud to have it,” Rosendale spokesman Shane Scanlon said in a statement. “Matt and the NRA have never discussed anything beyond the organization’s membership and endorsement process.”

Asked what Rosendale meant by the NRA “coming in” to the race, Scanlon maintained that the candidate was referring to an endorsement rather than an ad.

“This is no different than Jon Tester walking into UAW and asking for their endorsement and then being told he’s likely going to get it,” he said.

Lars Dalseide, an NRA-ILA spokesman, also denied that the group discussed any ads with Rosendale or his campaign.

“Any assertion otherwise is completely false,” he said.

Montana is rated by the Cook Political Report as likely to remain in Democratic hands this November. Even so, the race is one of the most closely watched in the country, and Tester has his work cut out for him: The state backed Trump by more than 20 percentage points in 2016, and the president has visited twice to campaign for Rosendale.