WASHINGTON – President Donald Trump's acting chief of staff Mick Mulvaney, a former congressman who served multiple roles at the White House, is leaving his job and the president is appointing Rep. Mark Meadows to fill the powerful position.

Trump announced the moves in a series of tweets late Friday night.

The shake up in the key White House role follows Trump's acquittal in his Senate impeachment trial and a recent push to appoint especially trusted allies to top jobs and to push out others whose allegiance to the president has been questioned.

"I am pleased to announce that Congressman Mark Meadows will become White House Chief of Staff. I have long known and worked with Mark, and the relationship is a very good one," Trump said in a tweet on Friday.

Trump thanked Mulvaney for "having served the Administration so well" and announced he would become the U.S. Special Envoy for Northern Ireland.

Meadows, 60, who has represented North Carolina in the House since 2013, announced last year that he would retire. A former chairman of the Freedom Caucus, Meadows has helped rally conservative House members on Trump's agenda, including on health care and tax cuts.

Meadows applauded the "incredible victories" of Trump's first three years and said in a statement he looked forward to "helping build on that success."

Mulvaney, a former South Carolina lawmaker who joined the Trump administration as the president's top budget aide in 2017, was Trump's third chief of staff – though he never shed the "acting" qualifier in his title, and Trump never explained why.

Widely seen as less hands-on with Trump than his predecessor, John Kelly, Mulvaney served in the role as the White House navigated through the president's impeachment and the controversy over the withholding of foreign aid to Ukraine. Mulvaney played a role in that controversy by seeking a legal justification to withhold the military aid.

Mulvaney was heavily criticized for a news conference in October in which he appeared to acknowledge that Trump withheld aid from Ukraine until it agreed to conduct an investigation involving domestic politics in the U.S. The House impeachment managers repeatedly used Mulvaney's words against the White House during the trial.

"We do that all the time with foreign policy," he said at the time. "And I have news for everybody: Get over it. There’s going to be political influence in foreign policy."

Mulvaney later issued a written statement walking back his comments, saying Trump was strictly concerned about corruption in Ukraine.

Trump tapped Mulvaney in December 2018 to replace Kelly, a retired Marine Corps general who replaced Trump's first chief of staff – Reince Priebus – in 2017.

David Cohen, a political science professor at The University of Akron who studies the office of chief of staff, said it was clear the move had been in the works for some time given Meadows' decision not to run for reelection.

"Meadows clearly knows Congress and is a loyal protector of the president, so he brings that to the job," Cohen said. "But Trump has never empowered any of his chiefs with the tools to be effective. He is resistant to changing his leadership methods to allow for a strong chief of staff to run the White House. It is doubtful that he will start now."

The appointment was applauded by several conservative allies of the president's. Heritage Foundation President Kay C. James described Meadows as a "strong leader" and "principled conservative."

"Throughout his tenure in the House, Congressman Meadows represented his district honorably and became one of the most visible conservative lawmakers on Capitol Hill," James said. "His leadership of the House Freedom Caucus elevated conservative ideas and defenders of liberty."

Lynda Bennett, who was endorsed by Meadows, received the highest number of votes in the GOP primary election to replace him in his North Carolina's congressional district this week. But Bennett won less than 30% of the vote, meaning she will face a runoff in May.

Contributing: The Citizen Times