The co-founder of a company with close ties to the Clinton campaign and Democratic Party that created a scurrilous dossier on Donald Trump has agree to testify before the Senate Judiciary Committee.

Glenn Simpson will speak to the committee behind closed doors about the dossier, which was created by a former British intelligence agent, Richard Steele, that made sensational and salacious charges about Trump and Russia.

It is expected that Simpson will be asked about his company's close ties to Democrats as well as Fusion's work for individuals tied to the Russian government.

In exchange for his testimony, the committee will drop the subpoena it issued last week.

The Hill:

"However, since that time, Mr. Simpson, through his attorney, has agreed to provide a transcribed interview and requested that the subpoena compelling his attendance at Wednesday’s hearing be waived," committee Chairman Chuck Grassley (R-Iowa) and Ranking Member Dianne Feinstein (D-Calif.) said in a statement.

"We’ve reached an agreement on this request and have withdrawn the subpoena," they added.

Fusion GPS came to the committee's attention after a dossier it had commissioned from a former British spy during the campaign was published. The dossier contains salacious allegations about Trump that haven't been verified.

Simpson had previously indicated he would take the Fifth rather than testify in an open hearing.

Chairman Grassley accused Fusion GPS of being an unregistered foreign agent for Russia.  Simpson denies that, but he had several meetings with Russians closely tied to the government, including the lawyer Natalia Veselnitskaya, who met with Donald Trump, Jr. last June.  It is believed that Fusion tried to smear Bill Browder, a client of Russian lawyer Sergei Magnitsky, who died while in a Russian prison.  Congress passed the Magnitsky Act, which forbids several high-level Russians from coming to the U.S. or using our banking system.  It is this act that so many Russians have been lobbying to repeal over the last few years.

Fusion tried to dig up dirt on Browder in order to discredit him.  But Browder fought back, giving an affidavit to the Justice Department accusing Fusion of acting in the interests of Russia without registering as a foreign lobbying company.

The fake dossier on Trump won't figure as prominently in the hearing as Fusion's Russian ties, as well as its cooperation with and open support for the Clinton campaign and other Democrats.