There were more than 1,000 new advertisers on the platform each month before July, when Mr. Musk’s feud with Twitter began to intensify and the number of new advertisers sank to 200.
In September, there were 668 new advertisers, MediaRadar found. Factors such as economic conditions most likely played a role in the exodus, as did uncertainty about Twitter’s ownership and content moderation policies, said Todd Krizelman, MediaRadar’s chief executive, in a statement.
“Clearly, this acquisition is challenging advertiser confidence,” said Mr. Krizelman. He added that Mr. Musk’s plans to look for revenue sources beyond ads could mitigate any damage caused by Madison Avenue.
Following Mr. Musk’s tweet, a coalition of civil rights and activist groups called a news conference to push for a global advertising boycott of Twitter.
Understand Elon Musk’s Twitter Takeover
“We are witnessing the real-time destruction of one of the world’s most powerful communications platforms,” said Nicole Gill, the executive director of the nonprofit group Accountable Tech, on the call. “Unless and until Musk can robustly enforce Twitter’s existing community standards, the platform is not safe for users or for advertisers.”
Angelo Carusone, the chief executive of the progressive nonprofit Media Matters for America, said on the call that he had worked on several efforts to use advertiser boycotts to pressure social media companies to clean up their platforms. Usually, he said, some of the advertisers he solicits will turn down his requests, saying that reaching potential customers is a higher priority than making a point to Silicon Valley.
But after the activist coalition reached out this week to Twitter’s top 20 advertisers, including Anheuser-Busch, Disney and Procter & Gamble, Mr. Carusone said all the companies he had been in contact with had said they were either considering a spending pause or were implementing one.