Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) in March. (Ricky Carioti/The Washington Post)

This post has been updated, 7:05 p.m.

On Wednesday, the Senate Judiciary Committee is set to finally hold the hearing that was derailed earlier this month by the unfolding scandal over a meeting between top Trump officials and a Russian lawyer.

When Chairman Charles E. Grassley (R-Iowa) gavels in the hearing, he will attempt to focus on its stated subject, the Foreign Agents Registration Act (FARA) and Fusion GPS, the opposition research firm that paid former MI6 spy Christopher Steele to collect intelligence on the Trump campaign’s ties with Russia. The dossier contained numerous allegations about Donald Trump and the campaign, some of them unsubstantiated. The hearing was set up to examine the firm’s separate work on a legal case involving the Magnitsky Act, a law to punish Russian human rights violators.

The law was named after Sergei Magnitsky, who was tortured and killed in a Russian prison in 2009 after uncovering a $230 million tax theft. He worked for William Browder, the head of Hermitage Capital Management, who will testify at the hearing.

In his testimony, Browder will accuse Fusion GPS and its founder Glenn Simpson of running a smear campaign against Magnitsky, in conjunction with Russian lawyer Natalia Veselnitskaya and Russian American lobbyist Rinat Akhmetshin. They were all allegedly working with the law firm Baker Hostetler to defend the Russian company Prevezon from charges it laundered funds stolen in the fraud Magnitsky uncovered.

“Veselnitskaya, through Baker Hostetler, hired Glenn Simpson of the firm Fusion GPS to conduct a smear campaign against me and Sergei Magnitsky in advance of congressional hearings on the Global Magnitsky Act,” Browder will testify. “He contacted a number of major newspapers and other publications to spread false information that Sergei Magnitsky was not murdered, was not a whistle-blower and was instead a criminal. They also spread false information that my presentations to lawmakers around the world were untrue.”

If Fusion GPS was lobbying on behalf of the Russian government without registering as a foreign agent, that would violate FARA, Browder argues. He also accuses Veselnitskaya and Akhmetshin of setting up a nongovernmental organization called the Human Rights Accountability Global Initiative Foundation to lobby against the Magnitsky Act under the guise of discussing the issue of Russia’s ban on American adoptions.

“I hope that my story will help you understand the methods of Russian operatives in Washington and how they use U.S. enablers to achieve major foreign policy goals without disclosing those interests,” Browder’s statement reads. “I also hope that this story and others like it may lead to a change in the FARA enforcement regime in the future.”

Simpson was served a subpoena on July 21 demanding that he testify. Through his lawyers, he communicated his intention to invoke his right not to testify under the Fifth Amendment. On Tuesday, the Associated Press reported that Simpson had struck a deal to testify in private, avoiding a public questioning and negating his need to plead the Fifth.

Fusion GPS has denied that it was lobbying and has said it was simply doing legal research for Baker Hostetler on the Prevezon case, which settled in May with no admission of guilt by Prevezon.

Grassley’s interest in Fusion GPS is not solely about the Magnitsky Act. On March 27, he wrote to Fusion GPS to demand information about the Steele dossier and the FBI’s relationship to Steele. Four days later, Grassley wrote to the Justice Department about Fusion GPS, this time asking about the firm’s alleged lobbying against the Magnitsky Act. The hearing is meant to check on that Justice Department investigation.

The hearing had been postponed after the New York Times reported that Veselnitskaya and Akhmetshin had been two of the key members of a meeting with Donald Trump Jr., Jared Kushner and Paul Manafort at Trump Tower in June 2016. Fusion GPS has said it played no role in that meeting.

Nevertheless, Grassley and the committee’s ranking Democrat Dianne Feinstein (D-Calif.) tied the two issues together by calling on Trump Jr., Kushner and Manafort to testify at the hearing. Trump Jr. and Kushner struck deals to avoid having to testify openly. The committee initially thought it had a deal with Manafort, but it fell through and late Monday Grassley and Feinstein subpoenaed him.

Feinstein told reporters Tuesday afternoon she doubted Manafort would ultimately testify and that negotiations with his lawyer were ongoing. She said she wanted the hearing to get back to its original focus.

“The hearing was supposed to focus on FARA,” she said. “This is just an addition to it at the end.”

Update: Fusion GPS sent me the following statement after this article posted:

“Let’s be clear about what’s happening: The President’s political allies are going after Fusion GPS because it was reported to be the first to raise the alarm about the Trump campaign’s links with Russia.”