Based purely on what we know today from news reports and the steady stream of revelations coming from the House select committee investigating the attack, the attorney general has a powerful justification for a robust and forceful investigation into the former president and his inner circle. As White House chief of staff, Mark Meadows was intimately involved in the effort to overturn the election. He traveled to Georgia last December, where he apparently laid the groundwork for the phone call in which the president pressured Georgia’s secretary of state, Brad Raffensperger, to “find 11,780 votes.” Representative Jim Jordan of Ohio reportedly promoted a scheme to pressure Vice President Mike Pence to reject duly certified Joe Biden electors. And from their war room at the Willard Hotel, several members of the president’s inner circle hatched the legal strategy to overturn the results of the election.

The president himself sat back for three hours while his chief of staff was barraged with messages from members of Congress and Fox News hosts pleading with him to have Mr. Trump call off the armed mob whose violent passion he had inflamed. That evidence, on its own, may not be enough to convict the former president, but it is certainly enough to require a criminal investigation.