Jim Wareham, president and general manager of Valley News Live, confirmed that an ad launched by Majority PAC, a Democratic group working to defend the Democratic majority in the Senate, was taken off the air because Majority PAC was unable to prove one of its assertions.

The spot charges that Rep. Rick Berg (R-N.D.) spent taxpayer funds on "flying his private plane," "staying in luxury hotels" and "for mail to help his campaign."

That last line, Wareham said, was what caused the station to pull the ad. He said that Majority PAC was unable to provide independent verification of the claim.

Berg spokesman Chris Van Guilder accused Democrat Heidi HeitkampMary (Heidi) Kathryn HeitkampNorth Dakota rep: Trump wants me to run for Senate No room for amnesty in our government spending bill Trump bank nominee gets rough reception at confirmation hearing MORE and her party of "desperate" and "false attacks."

"Fading in recent polls, Heitkamp and her liberal allies have become increasingly desperate, resorting to false and personal attacks against Rick to avoid talking about the big issues in this election," he said in a statement.

However, Majority PAC spokesman Zach Gorin stood by the ad, asserting that "Berg did in fact shamefully use taxpayer dollars on himself, including on his private plane, on luxury hotels, and on mailers that boosted his campaign."

"He owes North Dakota taxpayers an apology and an explanation," he said in an email to The Hill.

Gorin cited an Associated Press report on a $190,000 expenditure from Berg's office on mailings that Democrats assert were campaign mailings as evidence to support the ad. Berg's office said they were constituent communications, meant to keep North Dakotans apprised of his work in Congress.

Majority PAC ran a different ad in its spot in an effort to avoid ceding any airspace this close to the election. But this is the second time in October a Democratic ad has been taken off the air due to inaccuracies -- the last ad pulled came from the Democratic Senatorial Campaign Committee.

That ad offered what Democrats consider evidence that Berg was tied to a real estate company that had mismanaged properties. The DSCC revised the line in question and relaunched it.

Berg is locked in a tight battle with Democrat Heidi Heitkamp for North Dakota's Senate seat, with most polling showing him slightly ahead. Despite the red-lean of the state, Heitkamp has run a strong campaign, and the most recent independent poll indicated they're statistically tied. The Hill rates this race a toss-up.