Even without his direct order, his indirect influence could serve his ends and leave those in his sights facing expensive, time-consuming legal proceedings or other high-stress inquiries.

The story of that period has a powerful resonance today as Mr. Trump, angered in part by the two federal and two state-level indictments of him since leaving office, threatens to carry out a campaign of retribution if he returns to the White House. He has signaled that a second Trump administration would be stocked not with people who served as guardrails during his first term, but with carefully vetted loyalists who would eagerly carry out his wishes.

Mr. Trump's efforts were so sustained and troubling to top West Wing aides that at least two of them took from the White House notes they had written that memorialized how he said he wanted to use the powers of the federal government against his rivals.

In a few of the cases where Mr. Trump wanted investigations, there was legitimate basis for action. But in many others, there was little or no legal justification. None resulted in a criminal conviction.

If elected again, he would also return to the White House bolstered by the Supreme Court's ruling in July that former presidents have broad immunity from prosecution for official acts taken while in office.

And now with the Roberts Court basically handing a President a get-out-of-jail-free card, there simply would be little any law enforcement agency could do against a POTUS who can literally do or order anything if he colors those decisions as part of his official presidential duties and powers. The President has virtually become a law unto his/herself, unanswerable to anyone but the electorate once every 4 years - unless destroying the constitutional mandate for elections also falls under these same unfettered presidential powers or through a complicit and pliable Congress.