Special Counsel Robert Mueller has reportedly looked into the dossier as part of his investigation into possible ties between Trump's campaign and Moscow.
The Hillary Clinton campaign and the Democratic National Committee helped to pay for the research behind a secret dossier on Donald Trump and his alleged ties to Russia during the 2016 presidential election, according to a report from The Washington Post published Tuesday evening.
The outlet, citing unnamed sources familiar with the dossier's funding, said Mark Elias, a lawyer representing the Clinton campaign and the DNC, hired the firm Fusion GPS to conduct the opposition research. Fusion in turn hired Christopher Steele, a former British intelligence officer with ties to U.S. intelligence agencies.
The research was funded until just before the election, according to the Post report. The Post's sources said that neither the Clinton campaign nor the DNC directed Steele's research, and stressed that he was a contractor for Fusion GPS.
HuffPost has reached out to the DNC for comment.
Opposition research is standard practice in American elections, and it's common for a campaign to hire an outside firm to investigate an opponent.
Not all opposition research is without scandal, however.
President Trump's son, Donald Trump Jr., came under fire this summer after The New York Times reported that he met with a Kremlin-connected Russian lawyer who promised to give him damaging information about Clinton. As The New York Times noted in July, it's unusual for such research to come from other governments.