Yet it’s far from certain that the famously tight-lipped former FBI director will offer anything close to a dramatic performance. There’s a real risk that tomorrow’s hearings could lead to an unsatisfying conclusion for Democrats, who are, for the second time this year, in the position of having placed all their metaphorical eggs in Mueller’s basket.

Pro-impeachment Democrats, after all, were disappointed in April, when the former special counsel opted not to charge the president with a crime, after they’d spent two years hyping the Mueller report and its potentially incriminating conclusions. Making matters worse for the party, Attorney General William Barr publicly offered his own spin on the findings before Mueller ever addressed the public, giving the president room to claim a complete and total vindication that the report itself doesn’t support.

Since then, Democratic lawmakers have continued their committee investigations into the president’s alleged obstruction of justice, and support for impeachment on the Hill and on the campaign trail has slowly continued to build, though House Speaker Nancy Pelosi, among others, remains in opposition. Pro-impeachment Democrats see tomorrow as a chance to counter arguments that the narrative around Mueller’s findings is already baked in, and that a sufficient amount of public support for impeachment can’t be won. Many of those Democrats are on the committees before which Mueller will appear: 15 out of 24 Democrats on Judiciary and seven out of 13 on Intelligence have publicly called for an impeachment inquiry to begin.

The public learned the facts “over a two-year period in dribs and drabs,” Representative Adam Schiff, the Intelligence Committee chairman, told my colleague Todd Purdum in a recent interview. Had that information “come out all at once in a report by a special counsel, I think the president would have been quickly forced from office.”

Read: Adam Schiff is back from the wilderness

Committee members are hoping that, through their questioning, they can prod Mueller to create digestible sound bites or shareable social-media moments for the folks watching at home. “The American public is very busy, and a 448-page, dense report is likely not something that every person is going to have the chance to read,” Dean told me. “It is our job to bring it to life for them.” And there is power in visuals, too: “A lot more people watched The Godfather the movie than read the book,” Representative Raja Krishnamoorthi of Illinois, a member of the Intelligence Committee, told me.

Krishnamoorthi is part of the other audience for Mueller’s testimony: the Democrats on Capitol Hill who have not yet called for impeachment. He told me he’s fully prepared to change his stance after tomorrow. “I’m keeping my mind wide open to what he has to say, because it’s that important,” Krishnamoorthi said. Representative Ro Khanna of California, who also hasn’t called for impeachment and isn’t on either committee, told me he wants his colleagues to ask two key questions so that he can better understand Mueller’s decision making. Democrats “need to ask Mueller in multiple ways whether he would have indicted the president if it weren’t for the president’s office,” he said, “or whether he anticipates that the evidence is sufficient that the president may face criminal proceedings [after] his time in office.” Either of those admissions “would be explosive” for him and for other persuadable viewers, Khanna said.