The candidate U.S. President Donald Trump was widely expected to pick as his new chief of staff is apparently out of the running for the high-profile White House job.

Nick Ayers, who is currently Vice President Mike Pence's chief of staff, tweeted his thanks to Trump and Pence on Sunday, but said he will be leaving the administration altogether.

"I will be departing at the end of the year but will work with the #MAGA team to advance the cause," Ayers wrote, referring to Trump Make America Great Again slogan.

Trump is said to be looking for someone who will remain in the White House at least through the 2020 re-election campaign, and wrote in his own tweet Sunday that he plans to make his decision "soon."

With Ayers declining the job, reports say the president is now considering Treasury Secretary Steve Mnuchin, Office of Management and Budget director Mick Mulvaney, or conservative Republican congressman Mark Meadows as his new chief of staff.

One of them -- or maybe someone else -- would replace John Kelly as the person who traditionally controls access to the Oval Office.

Trump announced Saturday that Kelly is leaving by the end of the month.

"John Kelly will be leaving – I don't know if I can say 'retiring.' But, he's a great guy," Trump told reporters on the White House South Lawn.

Asked if Kelly was forced out or if he resigned, White House economic advisor Larry Kudlow told Fox News Sunday "I don't know to be perfectly honest."

Kelly's imminent departure comes as no surprise. There had been speculation for months – which had grown more intense in recent days — that the former Marine general would soon exit amid a further chill between him and the president, a deterioration in a relationship that had never been described as overly warm.

"It would have been a bad fit for anybody. He was essentially tasked with mission impossible," says Professor David Cohen, a presidential historian at the University of Akron in Ohio. "Trump never gave him the tools to succeed in the job" in which the chief of staff is supposed to be empowered to speak for the president and to have unfettered authority in organizing the White House and instilling stability and order.

"The cause of the chaos is Donald Trump himself, who is never willing to be reined in by anybody," and considered Kelly and his predecessor, Reince Priebus, to be more "staff than chief," says Cohen, who is writing a book about White House chiefs of staff.

Although Trump has a reputation for a higher rate of staff turnover than previous administrations, Kelly's total time of 16 months in the job will not be unusually short in a high-stress position where two years is considered a decent run. Priebus lasted just six months.

Trump will soon have his third chief of staff in two years, a turnover rate for which he harshly criticized his predecessor Barack Obama in January 2012.

"There's a lot of burnout in the position," Cohen tells VOA. "More often than not the individual that's serving in that position can't wait to find a new position, in the president's Cabinet or maybe simply retiring from the rigors of the White House and a presidential administration."

The departing chief of staff, during his time inside the White House was "a force for order, clarity and good sense," says outgoing House Speaker Paul Ryan. "He is departing what is often a thankless job, but John Kelly has my eternal gratitude." (VOA)

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