I've often wandered if the ONLY time anyone thought of restoring the Republic, out loud at least, was after Caligula's assassination, as you note - surely, surely there were "incidents" during Augustus' reign, particularly after 23 BC or so, when people were unable to ignore the fact that the substance of Republican government was disappearing under the fact of Augustan autocracy. But what really amazes me is that I don't remember hearing all that much about conspiracies against Augustus. Have I read the wrong books? Or were there such efforts, later hushed up by Augustus' excellent propaganda machine?

The way we all chortled at the very idea, in Gladiator, that anyone could even consider restoring the Republic by the time of Marcus Aurelius . . . but when, as you say, DID that disappear?

It would make a great deal of sense to me that, after the police-state tactics of Sejanus and the lunacy of Caligula, there would be a struggle to return to the Republic . . . but interestingly, by the time Caligula bought it, there wasn't a living person who woul have actually known what the Republic had been like!