Glenn Simpson, the founder of research firm Fusion GPS - who commissioned former MI6 officer Christopher Steele to compile the dossier - testified to the Senate Judiciary Committee in August.
"After speaking with majority and minority committee staff for 10 hours, Glenn Simpson requested the transcript of his interview be released publicly". Earlier that year, the firm had been probing Trump for a conservative website funded by a GOP donor, but that client stopped paying for the work after it became clear Trump would win the GOP nomination, according to people familiar with the matter.
The publication of a controversial dossier about President Donald Trump's alleged links with Russian Federation, authored by a former MI6 spy, has already resulted in a death, it has been claimed.
Increasingly, the Democrats and Republicans on the committee are going in different directions - with Grassley moving to investigate matters involving Clinton when she was secretary of state and Feinstein concentrating on Russian interference in the 2016 election.
Democrats says those investigations are a distraction. "So, you know, that tells you something about somebody", Simpson said during the testimony, regarding Trump's relationship with Sater.
Simpson said only that the person had not been a source of Steele's, and that Simpson believed the person "was a voluntary source, someone who was concerned about the same concerns we had".
In the op-ed, Mr. Simpson and Mr. Fritsch said the transcripts would show that they told lawmakers that they believed the dossier had been taken seriously by the F.B.I. because it matched reports that the bureau was receiving from other sources.
Mr Trump has repeatedly denied colluding with Russian Federation during the campaign, and called the entire investigation a "witch hunt".
Ironically, both might be considered to be a step forward in government transparency, although, those members of the US Senate who did not want the 300 plus-page testimony to be released, might disagree.
"The only way to set the record straight is to make the transcript public", she said in a statement.
It was released by the ranking Democrat on the Senate Judiciary Committee, Sen.
Simpson had previously declined to answer another question posed by the committee's investigators, citing "security".
Fusion GPS was hired in mid-2016 by a lawyer for Hillary Clinton's presidential campaign and the Democratic National Committee to dig into Trump's background.
Fusion GPS, the Paul Singer-linked opposition research group behind the infamous phony Trump dossier, made payments to media companies as well as individual journalists, according to federal court documents.
Simpson told investigators that Steele is "basically a Boy Scout", saying he has worked with Steele on and off since 2009 and he knew him to be "a person who delivered quality work in very appropriate ways".