President Trump famously promised that, if elected president, he would “drain the swamp” – upending the culture in Washington that favors the well-connected.

It is special counsel Robert S. Mueller III whose work seems to be sending shock waves through the capital, by exposing the lucrative work in which lobbyists from both parties engage on behalf of foreign interests.

The Mueller probe has already claimed its first K Street casualty: Tony Podesta. His lobbying firm, the Podesta Group, a Washington icon of power and political influence, notified its employees recently that the enterprise is shutting its doors.

Since Mueller was appointed, more people and firms have either filed or amended registrations that make public their work on behalf of foreign interests than had done so over the same time period in each of at least the past 20 years. Lobbyists, lawyers and public relations professionals who work for foreign companies and governments say Mueller’s probe has spooked K Street, and that firms are likely to be more careful in their compliance with public disclosure standards.

“My colleagues are being contacted by waves of clients concerned about this,” said Joe Sandler, an ethics and lobbying lawyer in Washington who specializes in Foreign Agents Registration Act issues.

The Podesta Group was famous for providing access to Washington power, holding events for a roster of high-profile domestic and international clients who helped make it one of the city’s most successful lobbying firms. Revenue declined after the 2016 election, but the firm remained a powerhouse.

Tony Podesta, 74, the brother of longtime Democratic adviser and Hillary Clinton campaign chairman John Podesta, resigned on the day Mueller announced charges against former Trump campaign chairman Paul Manafort and his business partner Rick Gates.

The 12-count indictment included charges of failing to accurately report lobbying work for a Ukrainian political party as required under FARA. That section made reference to “Company A and Company B,” later confirmed to be the Podesta Group and Mercury, another lobbying dynamo that includes Vin Weber, a former Republican congressman from Minnesota who worked on the Ukraine account.

Mueller was appointed in May to investigate possible coordination between the Kremlin and the Trump campaign to influence the 2016 election, but his work and similar congressional inquiries have stretched into other areas. The charges against Manafort and Gates were unrelated to their Trump campaign work.

According to the indictment, the men used a Brussels-based nonprofit organization, the European Centre for a Modern Ukraine, to hide that they were running a multimillion-dollar lobbying campaign for a Ukrainian political party friendly to Russia. Mueller’s team alleged that the men hired the Podesta Group and Mercury to lobby for the Ukrainians in the United States.

According to the indictment, Gates told Mercury it would be “representing the government of Ukraine,” and provided talking points to the Podesta Group falsely describing how Manafort and Gates merely provided an introduction to connect them with the European Centre.