Facebook has allowed prominent Republican officials and candidates — including the chairman of the Senate Republican Conference — to use the platform’s powerful ad technologies to raise money by associating migrants with the surge of coronavirus infections in the southern United States.

The ads, whose central claim has been rejected by doctors and fact-checkers, illustrate the platform’s inconsistent approach to defining coronavirus misinformation, especially when elected officials are involved. Facebook’s management of misleading content is under intense scrutiny by the Biden administration as coronavirus case numbers climb again in the United States and health authorities grapple with the role of social media in shaping anti-vaccine attitudes. Biden raised alarm about the issue last month when he said in relation to Facebook, “They’re killing people.”

The latest test of the social media giant’s policies joins the inflamed debate over immigration to the life-or-death matter of the novel coronavirus.

“The CDC & Joe Biden are telling Americans to MASK UP but are letting THOUSANDS of COVID-19 positive illegal immigrants into our country!” warns an ad from Sen. John Barrasso (R-Wyo.), chairman of the Senate Republican Conference and a physician.

The ad, which began running on Aug. 6, has been viewed as many as 15,000 times, according to Facebook’s ad archive. It directs users to a petition calling on Biden to visit the southern border — and, ultimately, to a fundraising page benefiting the senator’s campaign committee, Friends of John Barrasso.

Similar ads — also asking for financial contributions and sponsored by multiple Republican members of Congress, candidates and super PACs — have blanketed the platform in recent days. Many represent congressional districts far from the southern border.

An ad from Sen. Kevin Cramer (R-N.D.) asserts that “thousands of unvaccinated illegal immigrants” enjoy more leniency than “American citizens” when it comes to health protocols. An ad from Rep. Ted Budd (R-N.C.) warns bluntly, “If Joe Biden really wanted to get COVID-19 under control in our country, he would address the crisis at our southern border. Letting unvaccinated ILLEGAL immigrants come into our country is a threat to American citizens.” And an ad from Rep. August Pfluger (R-Tex.) alleges, “Hundreds of thousands of migrants are pouring into Texas and thousands of them have tested positive for covid-19.” All the ads link to fundraising pages.

Cramer said his ad does not target immigrants and is instead a criticism of “Democratic leaders’ inconsistent liberal policies.”

“Open borders for immigrants with no demands for proof of vaccinations while proposing mandates on American citizens is gross hypocrisy,” he wrote in an email response to questions about his ad.

Lyssa Bell, a spokeswoman for Pfluger, said it was “beyond dispute thousands of covid-positive illegal migrants have been released into the interior of Texas.” Other lawmakers running such ads did not respond to requests for comment.

Facebook’s allowing the ads appears to be in conflict with the technology giant’s move last fall to remove ads from President Donald Trump’s reelection campaign asserting that accepting more refugees would exacerbate health risks related to the pandemic. At the time, Facebook representatives cited the company’s policy against hate speech.

“We rejected these ads because we don’t allow claims that people’s physical safety, health, or survival is threatened by people on the basis of their national origin or immigration status,” a Facebook spokesman said in September 2020.

Now, the claim has returned as Republicans seek to exact a political price from Biden for the largest migrant influx in at least two decades while also blaming him for the surge of coronavirus cases driven by the highly infectious delta variant.

Devon Kearns, a Facebook spokeswoman, said the ads run by the Republican officials do not violate the company’s policies. She drew a distinction with Trump’s claims last year by saying the new posts are “attacking unvaccinated people or potentially people with covid, which isn’t an attack on a protected group.”

The effort to tie the explosion of coronavirus cases to the arrival of migrants has gained currency among Republicans since it was articulated at a news conference and in a fundraising letter last week by Florida Gov. Ron DeSantis (R). But the claim rings false to health experts and fact-checkers, who note that border authorities are denying entry to people more easily than is possible under ordinary immigration law because of an emergency order put in place by Trump in March 2020; that people crossing the border are screened more rigorously for the coronavirus than are members of the general population; and that the positivity rate among migrants in McAllen, Tex., which is at the center of the outcry, is lower than in the surrounding county.

“Who knows if the politicians running these ads believe what they’re saying,” said Imran Ahmed, founder and chief executive of the Center for Countering Digital Hate, a nonprofit organization that examines online extremism. “But they know it pays to say they believe it. They’ve learned from all sorts of bad actors that you can monetize misinformation on social media.”

To fulfill its promise to clean up its platform, Ahmed said, Facebook should become more proactive in vetting paid posts, rather than “their default being to take every advertisement that someone wants to buy.”

“It’s a commercial consideration,” he added. “There is a tension between their promise not to be a vector for disinformation and their desire to maximize profits.”