“If @amazon ever had to pay fair taxes, its stock would crash and it would crumble like a paper bag. The @washingtonpost scam is saving it!” Mr. Trump tweeted in December 2015.

“The #AmazonWashingtonPost, sometimes referred to as the guardian of Amazon not paying internet taxes (which they should) is FAKE NEWS!” he wrote in June last year.

“Is Fake News Washington Post being used as a lobbyist weapon against Congress to keep Politicians from looking into Amazon no-tax monopoly?” he tweeted the next month.

How do the president’s broadsides play inside The Post’s newsroom?

“I don’t even know how to describe what goes through my mind,” Martin Baron, the paper’s executive editor, said in a telephone interview on Monday. “It’s completely made up.”

People close to the president have said critical articles in The Post often trigger his public musings about Amazon. Last week, after The Post followed up on a story broken by The New York Times that Mr. Trump’s lawyer had raised the prospect of offering pardons to two of Mr. Trump’s former top advisers, Michael Flynn and Paul J. Manafort, Mr. Trump fired off a tweet saying that Amazon did not pay enough taxes and was “putting many thousands of retailers out of business.”