President Trump ousted his Chief of Staff Mick Mulvaney on Friday night, replacing his controversial right-hand man with Rep. Mark Meadows (R-NC).

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

The president announced that Mulvaney will be shuttled off to Northern Ireland as a U.S. Special Envoy—a move that now also leaves open the position of the Director of the Office of Management and Budget, which Mulvaney oversaw. The shake-up comes as Trump’s White House faces daunting challenges, including a growing number of coronavirus infections, an economy bracing for the potential pandemic, and a re-election campaign.

“I want to thank Acting Chief Mick Mulvaney for having served the Administration so well,” Trump wrote.

Trump’s White House has seen an unusually fast churn through chiefs of staff. Meadows will become Trump’s fourth chief of staff in a little more than three years, after Reince Priebus, John Kelly, and Mulvaney. Trump publicly fired Priebus via tweet, while Kelly called the position “the hardest job I’ve ever had.”

Trump never dropped the temporary “acting” designation from Mulvaney’s title, even though Mulvaney didn’t require Senate approval for the position. Last June, Trump kicked Mulvaney out of the room during a television interview after his chief of staff coughed, saying, “you know I don’t like that.”

Mulvaney was informed of his ouster on Friday, according to The New York Times, as he visited Nevada amid the coronavirus outbreak.

An administration official told The Daily Beast, “He was not fired by tweet. Mick knew this was coming, [he] was not caught off guard or anything. He wishes Rep. Meadows the best.”

Mulvaney was deeply embroiled in the president’s long impeachment scandal. Two witnesses, who testified before lawmakers in the impeachment probe against Trump, claimed Mulvaney was directly involved in the administration's effort to have investigations launched in Ukraine in exchange for a meeting with Trump.

Fiona Hill, the former top Russia advisor to Trump, told lawmakers she had heard Gordon Sondland—former U.S. Ambassador to the European Union—state that there was an “an agreement with the Chief of Staff for a meeting if these 'investigations in the energy sector start.’” The “investigations” referred to a probe into Burisma Holdings, a Ukrainian gas company where former Vice President Joe Biden's son Hunter was a board member.

“ He was not fired by tweet. Mick knew this was coming. ”

Lt. Colonel Alexander Vindman, director for Eurasian affairs at the State Department, also claimed Sondland said Mulvaney was coordinating the meeting in exchange for the investigation into the Bidens.

Mulvaney also admitted to the U.S. withholding aid to Ukraine to pressure the country's president to look into a conspiracy theory about Democratic meddling in the 2016 election.

“Did [President Trump] also mention to me in passing the corruption related to the DNC server? Absolutely—no question about that. That’s it, and that’s why we held up the money,” he told reporters late last year. “What happened in 2016 certainly was part of the thing that he was worried about in corruption with that nation, and that is absolutely appropriate.”

After the press conference, Fox News’ Sean Hannity called him “dumb” while Republican strategist Terry Sullivan claimed the then-chief of staff was only “about 70 percent as smart as he thinks he is.”

Meadows, on the other hand, said Mulvaney was “doing a good job.”

In the House, Meadows is best known as the head of the staunchly conservative Freedom Caucus. Meadows announced in December 2019 that he wouldn’t run for re-election to his House seat.

The House Ethics Committee rebuked Meadows in 2018 over his handling of sexual harassment complaints from six staffers against a top aide. While Meadows fired the staffer, he paid him for four months after he left the position, according to a House investigation. The Ethics Committee eventually fined Meadows $40,000 for keeping the staffer on his payroll.

Meadows had previously expressed his desire to become Trump’s chief of staff. After Kelly announced in 2018 that he would leave the position at the end of that year, Meadows told reporters he would be “interested” in the role.

The rise of Meadows marks President Trump’s fourth chief of staff within his first term. When President Obama hit three chiefs of staff within three years, Trump took to Twitter.

“3 Chief of Staffs in less than 3 years of being President: Part of the reason why [Obama] can't manage to pass his agenda,” he wrote in a 2012 tweet.