President Donald Trump tweeted on Sunday that he has never seen so much “anger & unity” among Republicans over the “lack of investigation” into Hillary Clinton’s connection to a dossier developed in the 2016 presidential race to smear him.

Trump made the comments after Rep. Trey Gowdy (R-SC), chairman of the House Oversight committee, said on Fox News Sunday that he has concerns over Hillary’s campaign paying a law firm over $12 million for the dossier.

On October 24, The Washington Post dropped a bombshell that the DNC and Hillary’s campaign funded the now-debunked dossier. An unknown Republican donor first funded the dossier, produced by Fusion GPS through the GOP primary. It switched to the other side after that:

[Hillary campaign lawyer Marc] Elias and his law firm, Perkins Coie, retained the firm in April 2016 on behalf of the Clinton campaign and the DNC. Prior to that agreement, Fusion GPS’s research into Trump was funded by a still unknown Republican client during the GOP primary.

The Clinton campaign and the DNC through the law firm continued to fund Fusion GPS’s research through the end of October 2016, days before Election Day.

The next day, the non-partisan Campaign Legal Center filed a complaint with the Federal Election Commission (FEC) that claims Hillary’s campaign and the DNC violated campaign finance law over payments for the Trump Dossier. LawNewz reported:

According to a recent reports in the media, Marc Elias, who also served as the Clinton campaign lawyer, paid opposition research firm Fusion GPS to produce the dossier which exposed alleged connection between Donald Trump and Russia government. It also contained salacious allegations about Trump’s personal escapades. According to reports, the Hillary for America campaign paid for the research but routed the payments through Elias’ law firm Perkins Coie and described the purpose of the money as “legal services” on their FEC disclosures. The DNC and the Clinton campaign reported dozens of payments totaling more that $12 million dollars to Perkins Coie over the course of the campaign.

“By filing misleading reports, the DNC and Clinton campaign undermined the vital public information role of campaign disclosures,” said Adav Noti, with the Campaign Legal Center in a statement obtained by LawNewz. Noti previously served as the FEC’s Associate General Counsel for Policy. “Voters need campaign disclosure laws to be enforced so they can hold candidates accountable for how they raise and spend money. The FEC must investigate this apparent violation and take appropriate action.”

Gowdy is determined to get to the bottom of the dossier funding because if Hillary and the DNC funded it, then “it should not have been used for government investigations unless there was some serious corroboration of the details.” Gowdy continued, according to The Washington Examiner:

“If they relied on that dossier and they didn’t corroborate it or vet it, then we have a serious issue and that’s the next thing that House intel is trying to find out, whether or not the U.S. government relied on it,” he said.

“That’s the most important thing to me is how unserious the Democrats in the house have been about uncovering all of the facts,” he said. “I am interested in who paid for the dossier because that helps you understand motive and intent and whether or not you can rely on the document. I am much more interested in whether or not the Department of Justice and the FBI relied upon that dossier and initiating a counterintelligence investigation or in court findings.”

Gowdy mentioned that the Democrats in the House “have been ‘unserious’ about uncovering the details of the dossier, how it was developed, and who paid for it.”