President Donald Trump speaks to members of the press Friday after stepping off Marine One on the South Lawn of the White House in Washington. Credit: Patrick Semansky | AP

President Donald Trump lashed out at former Nixon White House counsel John Dean III, calling him a “sleazebag” ahead of his planned appearance at a House hearing Monday on the findings of special counsel Robert Mueller.

In tweets, Trump also took aim at House Democrats for continuing to focus on the report by Mueller that details findings of his investigation into Russian interference in the 2016 presidential election as well as possible episodes of obstruction of the probe by Trump.

Dean, whose congressional testimony in 1973 was key to the demise of President Richard Nixon, has frequently criticized Trump’s actions related to the Russian probe in his role as a CNN contributor.

In tweets Sunday night that he retweeted early Monday, Trump claimed that Democrats were “devastated” by Mueller’s findings.

“The Mueller Report was a disaster for them,” Trump wrote. “But they want a Redo, or Do Over. They are even bringing in @CNN sleazebag attorney John Dean. Sorry, no Do Overs – Go back to work!”

Monday’s hearing, convened by House Judiciary Committee Chairman Jerrold Nadler, D-New York, is billed as: “Lessons from the Mueller Report: Presidential Obstruction and Other Crimes.” Besides Dean, two former U.S. attorneys and a legal scholar are scheduled to appear.

A growing number of Democrats have called for launching an impeachment inquiry against Trump, while House Speaker Nancy Pelosi, D-California, has continued to counsel a more deliberate course.

In public remarks May 29, Mueller said his office could not consider whether to charge Trump with a crime because of a long-standing Justice Department opinion that a sitting president cannot be indicted. Mueller, who resigned as special counsel the same day, repeated a line in his report explaining that his team would have exonerated Trump of obstruction if it could have.

That remark emboldened Democrats who would like to see impeachment proceedings launched, despite a determination by Attorney General William Barr that Trump’s actions did not warrant obstruction charges.

White House counselor Kellyanne Conway also took aim at Dean on Monday during an interview on Fox News’ “Fox & Friends.”

“They’re picking their lawyers from TV now,” she said of the House Democrats, adding that Dean had spoken out against Trump’s nomination of Brett M. Kavanaugh for the Supreme Court.

“He’s not a credible person,” Conway said of Dean.

House Republicans had already started trying to discredit Dean as a witness before Trump’s tweets. For his role in the Watergate scandal, Dean pleaded guilty to obstructing justice and later was disbarred and served four months in federal prison.

“So let me get this straight,” Rep. Jim Jordan, R-Ohio, a Trump ally, wrote in a tweet last week. “The DOJ determined that President Trump did not obstruct Justice. But to make the case that he did, @RepJerryNadler is bringing in John Dean, who was actually found guilty of obstructing justice and was disbarred as a result!”