By these standards, the facts in Mueller’s report condemn Trump even more than the report’s refusal to clear him of a crime. Charged with faithfully executing the laws, the president is, in effect, the nation’s highest law enforcement officer. Yet Mueller’s investigation “found multiple acts by the President that were capable of executing undue influence over law enforcement investigations.”

Trump tried to “limit the scope of the investigation.” He tried to discourage witnesses from cooperating with the government through “suggestions of possible future pardons.” He engaged in “direct and indirect contacts with witnesses with the potential to influence their testimony.” A fair reading of the special counsel’s narrative is that “the likely effect” of these acts was “to intimidate witnesses or to alter their testimony,” with the result that “the justice system’s integrity [was] threatened.” Page after page, act after act, Mueller’s report describes a relentless torrent of such obstructive activity by Trump.

Contrast poor Richard M. Nixon. He was almost certain to be impeached, and removed from office, after the infamous “smoking gun” tape came out. On that tape, the president is heard directing his chief of staff to get the CIA director, Richard Helms, to tell the FBI “don’t go any further into this case” — Watergate — for national security reasons. That order never went anywhere, because Helms ignored it.

[Jennifer Rubin: Five questions that still need to be answered in the Mueller report]

Other than that, Nixon was mostly passive — at least compared with Trump.