An 11th candidate, Representative Eric Swalwell of California — a member of the House Judiciary Committee, which has the authority to begin such proceedings — has said he is “preparing for impeachment” and called it potentially “the only road to save our country.”

But several leading candidates were more hesitant on Wednesday. A representative for former Vice President Joseph R. Biden Jr. said in a statement that Mr. Biden “agrees with Speaker Pelosi that no one would relish what would certainly be a divisive impeachment process, but that it may be unavoidable if this administration continues on its path.” As he left a campaign event in Dallas on Wednesday, Mr. Biden did not stop to engage a sizable group of reporters who shouted questions about Mr. Mueller toward him.

Senator Bernie Sanders of Vermont, too, avoided an outright endorsement of beginning impeachment proceedings, but tweeted, “If the House Judiciary Committee deems it necessary, I will support their decision.”

The ground has shifted since the Justice Department released its redacted version of Mr. Mueller’s report. While a few candidates, including Ms. Warren, called for impeachment then, they were in the minority, and officials on other campaigns said there had been little pressure from voters.

(Ms. Warren, for her part, said on “The View” on Thursday that if Mr. Trump “were anyone other than president of the United States, he would be in handcuffs and indicted.”)