About 25 years ago, the column Straight Dope fielded this question: "Among other things, Richard Nixon qualifies as an ex-president. Has anybody given any thought to what will happen when he dies? Will flags be automatically be lower to half-staff, or will we have a big brouhaha about the appropriate procedure for mourning disgraced public leaders?"
The answer, in part: "This particular hot potato will be dropped into the lap of the man lucky enough to be president when Nixon kicks. It's not tradition, but a presidential proclamation that establishes the customary 30 days' public mourning. Conceivably, whoever's in charge could declare a national 30-day period of embarrassed throat-clearing, or choose to ignore the whole thing."
In the event, 20 years after the Watergate scandal, nothing of the kind happened. Nixon received his full posthumous due as a former president, including flags at half-staff, the offer of lying in state at the Capitol (his family declined), and a 21-gun salute and a generous eulogy from President Clinton at the funeral -- "He had an incredibly sharp and vigorous and rigorous mind," the president said about his predecessor, among other things.
Of course, not everyone was so laudatory -- "a hubris-crazed monster from the bowels of the American dream with a heart full of hate and an overweening lust to be President," was the gonzo thumbnail of Nixon's character, though not one offered to the public during the official funeral ceremonies.