In this Feb. 22, 2018, file photo White House counsel Don McGahn speaks at the Conservative Political Action Conference (CPAC), at National Harbor, Md. McGahn was barely on speaking terms with President Donald Trump when he left the White House last fall. Credit: Jacquelyn Martin | AP

The demand of Democrats on the House Judiciary Committee for live testimony by former White House Counsel Donald McGahn reminds me of the questions from college students that drive professors nuts — such as, “How much does the final exam count for?”

Generations of long-suffering instructors have responded with the same answer: “It’s in the syllabus.”

Likewise, what Democrats supposedly want to know from McGahn is in the syllabus — or, in this case, the 448-page report by special counsel Roberts S. Mueller III. The report describes in detail McGahn’s eyebrow-raising interactions with Trump, including this blockbuster:

“On June 17, 2017, the President called McGahn at home and directed him to call the Acting Attorney General and say that the Special Counsel had conflicts of interest and must be removed. McGahn did not carry out the direction, however, deciding that he would resign rather than trigger what he regarded as a potential Saturday Night Massacre.” (Trump has denied that he instructed McGahn to fire Mueller, a claim that earned him four Pinocchios from the Washington Post’s fact-checker.)

McGahn is not ready for his congressional closeup. On Tuesday, he failed to show at a committee hearing, despite having been subpoenaed. Chairman Jerrold Nadler, D-New York, warned that McGahn would be cited by the panel for contempt of Congress.

In defending a Justice Department opinion holding that McGahn can’t be forced to testify before Congress, White House Press Secretary Sarah Sanders noted that Mueller and his team conducted “hours and hours of interviews from White House officials, including more than 30 hours from former Counsel to the President, Don McGahn.”

That’s a lot of evidence, even if you don’t agree with the White House that it makes live testimony by McGahn inappropriate. So why do Democrats insist on bringing McGahn before the committee? (Presumably their goal is not to afford their Republican colleagues an opportunity to try to discredit McGahn.)

Former federal prosecutor Harry Litman offers a plausible answer.

Writing in the Washington Post earlier this month, Litman noted: “McGahn is already locked into an account of Trump’s conduct that appears to amount to multiple felonies for obstruction of justice. Detailing that conduct in a congressional hearing would provide a moment of drama akin to John Dean’s Watergate testimony. And it is that sort of drama that seems to be the Democrats’ only hope for putting impeachment into serious play.”

Actually, House Democrats are still arguing among themselves about whether to put impeachment “into serious play,” with Speaker Nancy Pelosi apparently adhering, for now, to a more cautious approach. But even if McGahn were to testify publicly as part of a “stealth” impeachment process, his presence would send a powerful message that mere words in a written report — one that few Americans have read — just can’t convey.

Michael McGough is the Los Angeles Times’ senior editorial writer, based in Washington, D.C.