CHARLESTON, S.C. — Democratic presidential candidates wasted no time Friday evening demanding the immediate public release of the long-awaited report from Robert S. Mueller III, with several saying that Americans deserved to know any findings about President Trump, Russia and the 2016 election in order to form judgments about Mr. Trump and the 2020 race.

Former Representative Beto O’Rourke, campaigning in South Carolina on Friday night, told reporters that “those facts, that truth, needs to be laid out for all Americans to be able to make informed decisions going forward, whether at the ballot box” or in their discussions with their senators and representatives.

Mr. O’Rourke, asked if he supported impeaching Mr. Trump, said he believed the president and his 2016 campaign “at least sought to collude with the Russian government to undermine our democracy” and that Mr. Trump “sought to obstruct justice” once in office.

“I think those are grounds enough for members of the House to bring up the issue of impeachment,” he said. “But whether they do or not, this will ultimately be decided by the American public at the ballot box in South Carolina and in every state of the union.”