WASHINGTON — Special counsel Robert Mueller’s public remarks on Wednesday kicked off a new surge of Democrats calling for impeachment proceedings to begin against President Trump.

Progressives in the House and contenders for the party’s 2020 presidential bid are the two loudest voices calling for impeachment, as House Speaker Nancy Pelosi continues to call for caution.

Mueller poured more fuel on that fire Wednesday when he reiterated what he had written in his report: that his office could not charge Trump with a crime because that is a role for Congress, not the Department of Justice.

“Under longstanding department policy, a present president cannot be charged with a federal crime while he is in office. That is unconstitutional,” he said. “The Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing.”

Several Democrats took this as an implicit — or explicit – referral to Congress to begin impeachment proceedings.

New Jersey Sen. Cory Booker, who is seeking his party’s nomination for president, became the latest Democrat to say Congress has “a legal and moral obligation to begin impeachment proceedings immediately.” Booker had previously called only for further investigation by relevant committees.

Vermont Sen. Bernie Sanders said he'd leave the decision up to the House Judiciary Committee, but if it were to begin impeachment proceedings, he would "support their decision to do so."

Other Democrats running for president in 2020 who had previously called for impeachment proceedings took Mueller’s public statement as yet another call to action.

“What Robert Mueller basically did was return an impeachment referral,” California Sen. Kamala Harris tweeted. “We need to start impeachment proceedings. It's our constitutional obligation.”

Former Texas representative Beto O’Rourke called for impeachment proceedings to begin because “there must be consequences, accountability, and justice.” Elizabeth Warren, Julián Castro, and Pete Buttigieg are among the other presidential hopefuls calling to begin impeachment proceedings. Seth Moulton, a member of the House and a 2020 candidate, said that Congress should begin proceedings "tomorrow."

New York Sen. Kirsten Gillibrand had endorsed Pelosi's stance earlier this month, but on Wednesday said it is time to begin impeachment proceedings. Former vice president Joe Biden, however, was more restrained. His spokesperson said that Biden "agrees with Speaker Pelosi that no one would relish what would certainly be a divisive impeachment process," but that Congress should continue to investigate Trump.