The ad, "Explain," features North Dakotan Robert Trefethren, who explains that though he didn't go to college, he wants to send his sons, but can only do so with college aid.

"Rick Berg is worth $24 million, but voted to cut college aid to pay for a tax break for millionaires like himself," he says directly to the camera.

Trefethren has a son of the same name who works for works for the North Dakota Democratic-NPL Party as a field organizer, but it was unclear whether he was involved in the ad at all, as he's not pictured. ND Democratic-NPL Party spokeswoman Rania Batrice said that the small size of North Dakota and the political spheres within it means interactions like these are common.

The use of local North Dakotans and the focus on Berg's wealth are tactics the Heitkamp campaign has used before in ads and on the campaign trail. But the mention of his wealth parallels a push from the Heitkamp campaign to focus on Berg's business background in an effort to turn one of his greatest assets into a liability.

Heitkamp and state Democrats have hammered Berg over the past few weeks for what they say is his connection to a company called Goldmark Property Management, which has a history of mismanaging residential buildings.

Berg insists that he has had no involvement with the company, and Heitkamp has not yet produced legal documents linking him directly to it, but he has been involved with companies related to Goldmark and was cited as a spokesman for the company in news reports.

It's the hope of Democrats that raising enough suspicion about Berg's business record could weaken him enough to provide them with a win, once seen as an unlikely outcome in the red-leaning state but something that Democrats believe is increasingly possible.

Watch the ad:

--This piece was published at 12:48 p.m. and updated at 5 p.m.