Writer Tony Schwartz, who claims he ghost wrote President Donald Trump’s 1987 memoir “Art of the Deal,” thinks he will resign by the end of the year.

“I still believe (and pray) Trump will resign by year end to avoid worse humiliation - e.g.indictment by Mueller, or 25th amendment removal,” the author tweeted Thursday.

Schwartz’s tweet comes on the heels of a Vanity Fair piece that quoted sources in and around the White House that questioned Trump’s temperament. The piece said that some cabinet members, including former White House Chief Strategist Steve Bannon, feared that Trump could be removed from office through the provisions of the 25th amendment.

The amendment provides a way for the president to be removed by the Vice President and Congress or heads of executive departments for being unable to discharge their powers. Advisers in Trump’s case were concerned that his behavior could be the cause for removal. Trump reportedly didn’t know what the 25th amendment was when Bannon spoke to him about it.

The Trump administration is also under several investigations stemming from accusations of collusion with Russia during the election and obstruction of Justice. Robert Mueller was assigned as a special prosecutor by the Justice Department to investigate Trump and his administration in May.