(CNN) A Republican Senate candidate in Montana is facing questions over comments he made suggesting he knew of the National Rifle Association's plans to be involved in his race -- a move that experts say could violate campaign finance laws meant to prohibit campaigns from coordinating with outside groups.

The comments, recorded on audio first published by the Daily Beast and subsequently obtained by CNN, features the candidate, Matt Rosendale, talking about Chris Cox, a chief strategist with the NRA's Institute for Legislative Action, and the group's plans to support his challenge against Democratic Sen. Jon Tester, a red-state incumbent up for re-election in the fall.

The Tester-Rosendale race is one of the most closely watched Senate contests in the country, with Rosendale looking to capitalize on Donald Trump's popularity in a state the President won by 20 percentage points in 2016.

"Outside groups are spending on your behalf?" an unidentified questioner asks Rosendale in the audio.

"Yes," Rosendale answers. "So the Club for Growth has already started. There's another group that has already started. I can't even remember the name of it now. They just started recently. So outside groups already started to come in. And I fully expect that the US Chamber's going to come in, and I fully expect the NRA is going to come in. I think both of them will be coming in, probably, right here in August sometime."

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