Colorado Republican Rep. Mike Coffman is crying foul over an independent attack ad that insinuates that his campaign is being funded by shady foreigners and Wall Street crooks, insisting that Colorado TV stations pull the spot from the airwaves.

The ad, paid for by a group called CounterPAC, slams Coffman for not signing a pledge to reject so-called “dark money” contributions that can’t be traced. Coffman’s opponent, Democrat Andrew Romanoff has agreed to reject such funds, the ad claims.

It then goes on to speculate as to who is behind the Coffman campaign’s “six-figure campaign ads.”

“[B]ig tobacco? Russian oil billionaires? Too-big-to-jail Wall Street bankers? The owner of China’s largest casino? We don’t know – and that’s just how Mike Coffman wants it,” the narrator says.

Colorado TV stations have received cease and desist orders, claiming the ad violates campaign laws that prohibit false statements, although Denver’s 9News reported that none so far have stopped airing the ad.

“The CounterPAC advertisement includes patently false statements about illegal foreign national participation in a political campaign,” Coffman campaign wrote in the letter, according to 9News.

“This would be the equivalent of a campaign commercial suggesting that one of Nancy Pelosi’s many commercials supporting Andrew Romanoff through the Democratic Congressional Campaign Committee were funded by Vladimir Putin and [convicted Colorado mass murderer] Nathan Dunlap,” the letter continues. “Of course, Mike Coffman would never lower himself to the level of CounterPAC’s unethical campaign practices on behalf of Andrew Romanoff.”

CounterPAC is unbowed.

“The only spurious claim here is the Coffman campaign’s accusation that we’ve committed a criminal act by telling the truth to voters,” the group’s spokesman, Jim Greer, told the station, in a letter responding to Coffman’s cease and desist.

“CounterPAC does not claim [in the ad] to know exactly who is funding these types of undisclosed communications,” the response letter said.

It highlighted a six-figure ad bought on Coffman’s behalf by the U.S. Chamber of Commerce, which does not disclose its donors.

“Coffman might not like to admit it, but by tolerating secret money in his congressional campaign, he is allowing for the possibility that groups like these will influence the election,” CounterPAC’s response said.

9News reported that lawyers for the two sides continue to battle it out.

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