By the time Attorney General Jeff Sessions arrived at President Trump’s Mar-a-Lago resort for dinner one Saturday evening in March 2017, he had been receiving the presidential silent treatment for two days. Mr. Sessions had flown to Florida because Mr. Trump was refusing to take his calls about a pressing decision on his travel ban.

When they met, Mr. Trump was ready to talk — but not about the travel ban. His grievance was with Mr. Sessions: The president objected to his decision to recuse himself from the Russia investigation. Mr. Trump, who had told aides that he needed a loyalist overseeing the inquiry, berated Mr. Sessions and told him he should reverse his decision, an unusual and potentially inappropriate request.

Mr. Sessions refused.