John Dean (Watergate, 1973) and Oliver North (Iran-Contra, 1987) are the leaders when it comes to incendiary White House scandal testimony, at least until Thursday, when former F.B.I. Director James Comey will appear before the Senate Intelligence Committee to describe the tense interactions that led to his abrupt firing by President Donald Trump last month. Comey’s testimony has the potential to surpass these predecessors. Much depends on what Robert Mueller, the recently appointed special counsel, now in charge of the sprawling Trump-Russia investigation, has cleared Comey to discuss. Particulars of the F.B.I.’s work examining possible ties between the Trump campaign and Russian operatives will be off-limits. But this still leaves plenty of latitude—and it’s impossible to imagine the voluble Comey would have agreed to testify if he were limited to repeating only his name, rank, and serial number. “I wouldn’t expect that Jim is going to be sitting at a green-felt table with a list of boundaries given to him by special counsel,” says David N. Kelley, a longtime Comey legal colleague and friend.

Here are four questions likely to be posed at Thursday’s hearing, and how to understand Comey’s possible answers.

Mr. Comey, in the letter President Trump wrote informing you of your dismissal, he said that you told him on three separate occasions that he was not under investigation. Is that true?

While Comey probably won’t be able to address whether Trump—or other White House aides—made efforts to curtail the Russia investigation on occasions that have not already been reported, Comey will likely clarify whether he ever told Trump that the president was off the hook.

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His answer is crucial. If he flatly denies telling Trump any such thing, Comey will be accusing the president of lying. But Comey’s response will no doubt be more nuanced, drawing a distinction between whether his comments to Trump were in the context of a national security investigation or a criminal inquiry.

Benjamin Wittes has been a friend of Comey’s since 2004, when Wittes was an editorial writer for The Washington Post and Comey was deputy attorney general in the administration of President George W. Bush. Wittes is now the editor in chief of the blog Lawfare, but he could end up becoming a witness if there’s ever an obstruction of justice case against Trump: at a March lunch, Wittes says, Comey described his ongoing efforts to keep the White House from meddling in the F.B.I.’s work.