Mr. Wisenberg said he was struck by Mr. Mueller’s focus on establishing the president’s mind-set when he weighed whether to fire Mr. Comey, and potential steps like whether to oust Attorney General Jeff Sessions, pardon people charged by Mr. Mueller or force the Justice Department to dismiss the special counsel.
No Supreme Court precedent exists to guide Mr. Mueller on whether obstruction of justice can occur if a president exercises a constitutional power with a bad motive, like firing a subordinate to cover up a crime; Mr. Wisenberg counted himself among those who do not think it can. But Mr. Mueller’s questions, he said, suggest the special counsel has adopted a broader interpretation of the law.
Some of the questions may present an opportunity for Mr. Trump, however. Asking him to explain what he meant when he told NBC News that he was thinking about the Russia investigation when he decided to fire Mr. Comey, for example, would permit Mr. Trump to backpedal on the remark or explain it away, perhaps by saying he did not really mean it.
Alan M. Dershowitz, a Harvard Law School criminal law professor who has frequently defended Mr. Trump on television and is informally consulting with him, told CNN on Monday that he thought Mr. Trump could invoke executive privilege to refuse to answer questions about his thinking when he decided to exercise constitutional powers.
But the problem for Mr. Trump is that those questions, Mr. Dershowitz said, were the “easy” ones. By contrast, Mr. Trump could not invoke the privilege about events that took place before he became president, like his business dealings.
Several legal experts said it was unusual for prosecutors to give Mr. Trump a preview of the questions, speculating that Mr. Mueller was bending over backward to defang any accusations of overreach. Mr. Buell said the move might also be aimed at uncovering any disputes over executive privilege now so they do not disrupt an interview.
But he predicted that despite all the “posturing,” Mr. Trump would allow his lawyers to talk him out of sitting down with Mr. Mueller.
“The game,” he said, “is to appear to be interested and cooperating without doing so.”