Maybe even during Caligula or Nero.

You can look to the Stoics under Nero and the Flavians, the most notable figure of whom was Helvidius Priscus, proud, not to say loud mouthed, tribune of the Plebs under Nero, and admirer of Cassius and Brutus (which got him banished) and later bad mouthing of Vespasian (which got him executed). (Juvenal (V:36) writes that HP and his father in law Thrasea Paetus celebrated the two assassins' birthday, which presumably coincided - "Quale coronati Thrasea Hevidiusque bibebant Brutorum et Cassii natalibus). Thrasea was executed at this time, 66AD.)

HP's son, also called Helvidius Priscus, kept to his father's faith and he too was exiled and executed under Vespasian's son, the emperor Domitian (though in his case, it may have been a rude bit of writing that Domitian took exception to - Domitian had a dark sense of humor, and did not take kindly to being the butt of other people's jokes).

Unfortunately, in the case of father and son, the various whys and wherefores are a little vague. The source material - snippets of Suetonius, Tacitus, and Dio Cassius - make it difficult to decide if the father was calling for a return to the old republic or some kind of general personal freedom or just trying to restore some of the power that the senate had had before the principate. He may have had no problem with the principate under Augustus. Given the leeway afforded him under Vespasian, it seems that he and his crew were not thought that much of a real threat, but that after a time he became just too tiresome. Opinions vary. The son, perhaps he was moved by philosophy, perhaps by filial piety.

Any hopes they may have had for a return to the republic were pie in the sky.

(FWIW, James Madison used him as a pseudonym back in the day.)

I'll try to get back to this, but those are the names that come to mind off hand. Much has been written about them and the stoics during this period.

​

​