SAN FRANCISCO (Reuters) - A left-leaning political group is challenging Facebook’s policy not to fact-check some political ads by running a spot that falsely claims Republican Senator Lindsey Graham has endorsed the Green New Deal, a plan by prominent Democrats.

Facebook Inc FB.O has come under fire in recent weeks over its decision to not fact-check ads run by politicians. The new ad comes days after Green New Deal champion Representative Alexandria Ocasio-Cortez grilled Facebook CEO Mark Zuckerberg on whether his site would allow such an ad.

“Could I run ads targeting Republicans in primaries saying that they voted for the Green New Deal?,” Ocasio-Cortez asked the tech executive at a congressional hearing on Wednesday.

“Congresswoman, I don’t know the answer to that off the top of my head,” Zuckerberg replied. “I think probably.”

Facebook has drawn criticism over its ad policy from Democratic candidates running in the 2020 presidential election such as former Vice President Joe Biden and Senator Elizabeth Warren.

Last week, Zuckerberg said Facebook did not want to stifle political expression.

Facebook spokesman Tom Channick said that since the new ad came from a political action group, rather than a politician, it was eligible for review by the company’s third-party fact-checking partners.

A screengrab from a video shows U.S. Senator Lindsey Graham (R-SC) appearing in a Facebook ad run by a PAC called The Really Online Lefty League, which falsely claims that he supports the Green New Deal, in order to draw attention to issues around Facebook ad policies, October 25, 2019. The Really Online Lefty League/Facebook via REUTERS.

“We have sent it to them for review,” Channick told Reuters, adding that the ad would be removed if found to be false.

The new ad cycles through archive footage of Republicans such as former Presidents Ronald Reagan and Richard Nixon before splicing together two real videos of Graham to make it look as if he said, “We believe in the Green New Deal.” It also mentions the false endorsement in the ad text.

Senator Graham’s office said it was aware of the ad and confirmed the senator opposes the Green New Deal, a proposal championed by Ocasio-Cortez that would eliminate U.S. greenhouse gas emissions within a decade.

Graham has previously called the proposal a “disaster” and said it would “destroy the American economy.”

Adriel Hampton, treasurer of the group behind the ad, The Really Online Lefty League, said he came up with the idea to draw attention to the problems around false claims in online political advertising. He has spent $50 to show the ad online.

“There appears to be little to nothing to stop serious election manipulation through false advertising, and that’s bad for our democracy,” Hampton said in an email to Reuters.

Ahead of the November 2020 election, lawmakers have also expressed concerns over the spread of misinformation through manipulated video, particularly deepfakes, which use machine learning to create realistic content where a person appears to say or do something they did not.

The video of Graham was manually edited, Hampton said. “No deepfakes needed,” he said. “Very low-budget, very easy to do.”

He said that he intended the false claim to be obvious to spot by including the claim that Graham endorsed the Green New Deal in the ad’s text.

“While a lot of people think our ad is funny, we’ve seen a lot of folks taking it at face value, and THAT is alarming,” he added.