A real impeachment trial could provide grounds for a deeper investigative dive reconstructing not just Trump’s actions that day but also the roles of other important players.

A New York Times investigation has established that several GOP congressmen — notably Reps. Mo Brooks of Alabama and Andy Biggs and Paul A. Gosar of Arizona — had ties to groups involved in the insurrection, or promoted the “Stop the Steal” movement that culminated in the assault, and/or talked up the event itself.

Ornstein points out that interviewing people such as those under oath could establish what sorts of conversations they had with Trump leading up to and during the assault. They might refuse, and the legal situation would get murky, but this should at least be attempted.

A trial is also crucial to fleshing out Trump’s extraordinary misconduct. As a Post investigation established, members of Congress pleaded with the White House that day to get Trump to call off the mob. But, consumed with watching it all on TV, he was hard to reach and not initially receptive to such pleas.

Everything we know about Trump’s behind-the-scenes conduct is through anonymous sources and partial accounts. The only way to get “a full picture of what Trump did,” Ornstein says, “is with an impeachment trial.”