A dark-money group linked to Alexandria Ocasio-Cortez has spent about $20,000 on anti-Biden Facebook ads aimed at South Carolina voters.

It’s one of the first salvos of negative advertising in a primary race that’s otherwise remained mostly positive. The group, a 501(c)4 called Organize for Justice, uses a barely month-old Facebook page called “Watercooler Politics.” Organize for Justice is a sister organization to Justice Democrats, which is a liberal political action committee closely linked to Rep. Alexandria Ocasio-Cortez; the group even recruited AOC to run for office.

“Sometimes the candidate that seems like the safest choice isn’t the safest choice.” reads the ad on which Organize for Justice has spent the most money, at least $7,500, as of Monday.

In close second is an ad on which at least $5,500 has been spent, which reads: “The United States has the largest prison system in the world. As Senator, Joe Biden helped build it.”

Both ads have been shown about half a million times, if not more, to South Carolina voters since Dec. 19.

All of the ads link directly to news articles, sometimes months old, that support the ad’s argument. None of them appear to collect contact information or solicit donations—suggesting that the goal of the ads is to change South Carolina voters’ minds.

South Carolina is the fourth state to vote in the race to decide the Democratic nominee for US president, voting on Feb. 29. The state is seen as a stronghold for Biden—in large part because many of the state’s Democratic voters are African-Americans who, polls show, overwhelmingly support Biden.

It seems likely that the ads are meant to appeal to African-American voters in particular, based on the the prison-related message and also on an electability argument, factors many political strategists believe resonate with that demographic group. It’s not clear how Organize for Justice has used Facebook’s powerful targeting tools to seek its voters; Facebook doesn’t publish the choices that advertisers make.

Waleed Shahid, a spokesman for Organize for Justice said the ads were targeted to South Carolina Democrats generally. “I think Democrats in general care about racial justice and civil rights issues,” he said.

Other ads that Organize for Justice may have concluded were less successful at getting clicks—and thus, perhaps, changing minds and votes—focused on foreign policy; social security; and Anita Hill. Biden chaired the Senate Judiciary Committee when it harshly questioned Hill over her accusation of sexual harassment against Clarence Thomas, who, at the time in 1991, was being considered for a seat on the Supreme Court.” Joe Biden did a disservice to me. A disservice, more importantly, to the public,” reads the Anita Hill quote in Organize for Justice’s ad.

A few ads from Organize for Justice, on which very little money has been spent, criticize Pete Buttigieg and were targeted to Iowa voters. Shahid said the group was still testing its messages in Iowa, but planned to ramp up its ads shortly. In a press release sent after Quartz asked Organize for Justice about the ads, the group said it hoped to spend “at least half a million dollars on paid digital advertisements in the next two months.”

Justice Democrats has focused on primary challenges against less-liberal Democrats. Encouraging primary challenges against non-white members of Congress has earned Justice Democrats the ire of the Congressional Black Caucus.

Jeffrey Chester, director of the Center for Digital Democracy, told Quartz he thinks ads that target voters based on location should not be used. “All candidates should agree that they will not use data-driven ads without full disclosure of the techniques, spending and impact,” he wrote in an email.

Shahid, from Organize for Justice, said the ads were designed to “educate” voters about Biden and Buttigieg’s records. “Joe Biden is still the frontrunner in many national polls. He has a record that I don’t think voters have gotten to be as familiar with as they should be.” Shahid said the organization was looking into video advertisements on various platforms, potentially including YouTube.