An ad against Nebraska Senate Republican candidate Ben Sasse claiming the grassroots favorite supports Obamacare has gotten the attention of ForAmerica Chairman Brent Bozell, who condemned it as a Washington establishment attack and called on Senator Minority Leader Mitch McConnell to pull the ad.

The ad is from a super PAC run by two aides that are also running a pro-McConnell super PAC.

“This ad is beneath contempt, and I call on Mitch McConnell to rein in his Washington establishment hacks and pull this ad immediately,” Bozell said in a statement. The ad is running on Nebraska television and was created by the Freedom Pioneers Action Network, the super-PAC with close ties to Sen. McConnell. The PAC, while claiming to be independent, has received donations from a number of supports of Shane Osborn, who is considered the establishment favorite and is backed by Senators Lindsey Graham and John McCain

The ads, which the Super PAC is legally prohibited from coordinating with the Osborn campaign, are not the first in which supporters of Osborn have been called disingenuous. One campaign ad in which Osborn personally appears quotes an article from the Fremont Tribune in which Sasse is alleged to have supported Obamacare. The Tribune has since condemned the use of their name in the advertisement and implored Osborn to “be responsible. Don’t take comments out of context. Don’t gloss over the important background.”

Conversely, the Osborn campaign is attacking a PAC, the 60 Plus Association, for an ad attacking Osborn regarding a U.S. Navy memo a friend of Osborn’s wrote clearing his actions in a 2001 incident in China. An attorney acting in the Osborn campaign’s name has sent a letter to television stations running that ad requesting it be taken down.

Freedom Pioneers has spent upwards of $100,000 on attack ads against Sasse, and its webpage currently only displays a flyer-like front page condemning Sasse as an “Obamacare supporter.”

In his statement, Bozell makes clear he believes McConnell is behind the anti-Sasse push:

McConnell and the Washington establishment are throwing the kitchen sink at Ben Sasse; they’re terrified they’d have to put up with another principled conservative in the U.S. Senate. So now they’ve gone into the sewer to not only attack Ben, but his family as well. Fact: Ben Sasse will be a strong leader and voice in the Senate for Nebraskans who’ve had enough of Washington. Pull the plug and apologize.

While Osborn was for most of the race the frontrunner, Sasse began a slow surge in March that has now become a full-fledged lead, polling six points ahead of Osborn in a poll last month.