Having announced White House Chief of Staff John Kelly’s impending departure after months of rumors, President Trump learned on Sunday that Nick Ayers, his first choice to replace Kelly, has turned down the job.

Currently serving as chief of staff to Vice President Mike Pence, Ayers announced his decision to leave the White House at the end of the year in Trump style, via Twitter. Ayers had been expected to replace Kelly for weeks, reportedly with the support of the president’s daughter Ivanka and his son-in-law Jared Kushner.

Why Ayers chose to quit rather than accept a major promotion, he didn’t explain — but Trump’s mercurial behavior, the persistent maelstrom in the White House, and increasing pressure from the Russia investigation all are likely factors. Other candidates said to be in line for Kelly’s job include Rep. Mark Meadows (R-NC), a leader of the ultra-right House Freedom Caucus, and Mick Mulvaney, who now heads the Office of Management and Budget.

Kelly’s tenure is widely viewed as a failure to impose order in the chaotic Trump White House, although it is impossible to say whether matters would have been even worse in his absence. If Trump were consistent, he might have to assume responsibility for the rapid turnover in the highest position on his staff, since he will have appointed three chiefs of staff in under two years as president. He showed little sympathy in January 2012, when Barack Obama was enduring a similar but less acute personnel problem, tweeting:

News reports indicate that Trump may confront difficulty in persuading any qualified candidate to accept the job in the wake of Ayers’ rejection. As the Washington Post noted, the position that once made presidential bureaucrats into “Washington royalty” has become a professionally perilous, often humiliating and impossible task — as Kelly and his predecessor Reince Priebus, dismissed in a tweet, have both learned to their chagrin.