The top Republican witness at a contentious impeachment hearing says he was bombarded with threatening messages and demands he lose his job — even ­before the testimony was done.

George Washington University law professor Jonathan Turley earned the apparent enmity from giving testimony before the House Judiciary Committee in which he said impeaching President Trump was a bad idea.

“My call for greater civility and dialogue may have been the least successful argument I made to the committee,” Turley tweeted Thursday. “Before I finished my testimony, my home and office were inundated with threatening messages and demands that I be fired from GW.”

The wave of wrath pointed at Turley was just one episode in the week of impeachment drama that again dominated Capitol Hill.

Late Friday, President Trump’s top White House lawyer, Pat Cipollone, fired off a two-paragraph letter excoriating the impeachment probe as the deadline arrived for Trump to decide if he would send representatives to the House of Representatives as key hearing dates approach.

“[Y]our impeachment inquiry is completely baseless and has violated the basic principles of due process and fundamental fairness,” Cipollone claimed. “You should end this inquiry now and not waste even more time with hearings.”

The blistering letter did not explicitly say if the White House planned to send representatives to the hearing. However, White House officials later told news organizations they would not come.

“The White House said they wanted open hearings, not closed, and then they didn’t want those either,” fired back House Intelligence Committee chairman Adam Schiff (D-Calif.) on Twitter. “Then they said they wanted to participate in the proceedings, and now they say they don’t.”

The back-and-forth came a day after House Speaker Nancy Pelosi (D-Calif.) instructed senior Democrats to draft possible articles of impeachment. If approved, the bill would head to the Senate for a full hearing, which could end with Trump being removed from office.

Pelosi reversed her opposition to impeachment after learning of whistleblower allegations that Trump and his allies tried to pressure Ukrainian officials into investigating former Vice President Joe Biden’s son, Hunter.

Several current and former US officials testified that key military aid and a White House visit were held up as Trump and his allies pushed for a probe into Hunter Biden’s $50,000 a month gig on the board of a natural gas company there, Burisma.