On policy, Trump is making sudden decisions without much staff consultation, wagering that they will pay dividends — accepting North Korean leader Kim Jong Un’s invitation for a face-to-face meeting and threatening to veto before ultimately signing the most recent government spending bill.

On the stump, Trump is an improvisational showman. He swooped into the working-class Ohio town of Richfield on Thursday to pitch his infrastructure plan but diverged from his script to deliver surprise commentary on a medley of issues. He threatened to delay a newly renegotiated trade deal with South Korea and announced that the United States may soon withdraw troops from Syria.

The president’s unbridled eruptions continued Saturday in a pair of tweets hammering Amazon.com and falsely stating that “the Fake Washington Post” was acting as a lobbyist for the retail behemoth. The Washington Post operates independently of Amazon, though the newspaper is owned by Jeffrey P. Bezos, the founder and chief executive of Amazon.