When Facebook lifted its ban on political ads in Georgia, local News Feeds became dramatically more partisan and less informative, according to research published on Tuesday by The Markup.

Facebook banned US political advertising in the wake of the November 3rd presidential election as part of its broader effort to fight election misinformation. However, the platform partially lifted the ban on December 16th, allowing ads specific to the Georgia runoff on January 5th.

To study the effect of those ads, The Markup paid 58 Facebook users in Georgia to provide data on the content that appeared in their News Feeds in the weeks leading up to the runoff election. The resulting data (which is available on Github) showed a huge change in users’ feeds when Facebook reopened political advertising in Georgia.

When the ban was in place, most political content on users’ feeds was from news organizations like the Atlanta Journal-Constitution, CNN, or The Wall Street Journal. Once political ads were restored, that content was overwhelmed by paid political content from Raphael Warnock’s Senate campaign, VoteGOP, or other political groups.

Notably, The Markup also found a specific instance in which Facebook was paid to promote false claims. The report highlights a $25,000 ad buy from incumbent Senator David Perdue claiming his opponent, Jon Ossoff, “is China-bought and would provide our adversaries with just another way to threaten our national security.”

As a documentary filmmaker, Ossoff received some China-linked payments when two of his films were licensed for broadcast by a partially state-backed TV station in Hong Kong. But the broadcasts were only a small portion of the overall licensing business, and the claim that his campaign is funded or endorsed by the Chinese government has been labeled as false by fact-checkers.

Reached for comment, Facebook emphasized the relatively small part paid political content plays on its network, outside of exceptional events like the Georgia runoff. “In an election where millions of people have already voted, even this tiny sample size has reinforced a basic truth about politics: the closer you get to Election Day, the more political content everyone is likely to see – whether it’s online, in the mail or on TV or radio,” a representative told The Verge.

The report comes after multiple reports of demonstrably false ads being promoted by Facebook, often receiving promotion even after moderators had removed an earlier version of the ad.

Facebook has long struggled with political ad policies, particularly during the 2016 presidential election when a Russian influence operation successfully promoted multiple campaigns on the site. Competing platforms like Twitter have disallowed campaign ads entirely, but Mark Zuckerberg has defended the importance of allowing political ads on the platform on free speech grounds, telling investors, “I don’t think it’s right for private companies to censor politicians and the news.”

Update 2:15PM ET: Added statement from Facebook.