Mick Mulvaney, assistant to the president and acting chief of staff, the White House, speaks during the Milken Institute's 22nd annual Global Conference in Beverly Hills, Calif., April 30, 2019.
FILE - Mick Mulvaney, assistant to the president and acting chief of staff, the White House, speaks during the Milken Institute's 22nd annual Global Conference in Beverly Hills, Calif., April 30, 2019.

WASHINGTON - The White House on Sunday belittled Democratic lawmakers who are continuing to advance the case for impeaching President Donald Trump after former special counsel Robert Mueller failed to produce any explosive new allegations against the U.S. leader at last week's congressional hearings.

"This is not over in their minds, which is absolutely bizarre," acting White House chief of staff Mick Mulvaney told the Fox News Sunday interview show. "This is over. Most folks know it is over."

Mulvaney offered his comments two days after Congressman Jerrold Nadler, chairman of the House Judiciary Committee, said that "in effect" the panel has undertaken an impeachment inquiry of Trump.

FILE - Judiciary Committee Chairman Jerrold Nadler arrives for a House Democratic caucus meeting on Capitol Hill in Washington, July 10, 2019.

The House Democrats are looking into whether Trump obstructed justice by allegedly trying to impede Mueller's investigation into Russian meddling in the 2016 U.S. presidential election by asking key aides for help in ousting the prosecutor in the midst of his 22-month probe.

Nadler said his panel is filing suit in an effort to get a judge to approve release of secret grand jury testimony taken by Mueller's team of prosecutors during its probe, to build its impeachment case against Trump.

About 100 of the 235 Democrats in the House of Representatives have called for Trump's impeachment or the start of an impeachment inquiry, while the president has long condemned the investigation as a massive waste of time and says he has been cleared of wrongdoing.

FILE - Speaker of the House Nancy Pelosi, D-Calif., speaks during a news conference after hearings with former special counsel Robert Mueller, on Capitol Hill in Washington, July 24, 2019.

House Speaker Nancy Pelosi, while agreeing to Nadler's pursuit of the grand jury testimony, has blocked the formal opening of an impeachment inquiry. Instead, Pelosi, while not ruling out impeachment, has supported multiple House committee investigations of Trump, his links to Russia, his business affairs and his administration policies.

She and other cautious Democrats have voiced fears about the political repercussions of impeaching Trump, knowing that even if the 435-member House on a simple majority vote impeached Trump, the Republican-controlled Senate almost assuredly would not muster the two-thirds vote needed to oust him from office.  

Attorney General William Barr has decided no criminal charges are warranted against Trump, a decision that came after Mueller reached no conclusion on the obstruction question, while also not exonerating him.

FILE - Former special counsel Robert Mueller checks pages in the report as he testifies before the House Judiciary Committee hearing on his report on Russian election interference, on Capitol Hill, July 24, 2019.

Mueller told the congressional hearings that in any event longstanding Justice Department guidelines prohibited the indictment of a sitting U.S. president, although he said Trump could be charged once he leaves office.

Nadler told ABC News Sunday that his Judiciary panel already has impeachment resolutions ready for consideration or could draft new ones to send to the full House of Representatives, depending on what new information about Trump might be found in its ongoing investigation.

Mueller's six hours of testimony was often halting, with the prosecutor deflecting dozens of questions about the 448-page report on his investigation. Democratic and Republican lawmakers alike were often frustrated at his refusal to explain the conclusions he reached or disputing their partisan conclusions about the report findings.

Even so, Nadler said it was "very important" that Mueller testified.

"He broke the lie that the president and the attorney general have been saying to the American people," that Trump had been totally cleared, Nadler said.

A news ABC News-Ipsos survey showed American voters' views about impeaching Trump were little changed after the Mueller testimony, with 47% saying it made no difference, 27% that it made them more inclined to support impeachment and 26% less inclined.