Like his father-in-law, Thrasea Paetus, whose daughter Fannia he had taken as his second wife, Priscus was distinguished for his ardent and courageous republicanism. Although he repeatedly offended his rulers, he held several high offices. During Nero's reign he was quaestor of Achaea and tribune of the plebs ; he restored peace and order in Armenia, and gained the respect and confidence of the provincials. His declared sympathy with Brutus and Cassius occasioned his banishment in 66. Having been recalled to Rome by Galba in 68, he at once impeached Eprius Marcellus, the accuser of Thrasea Paetus, but dropped the charge, as the condemnation of Marcellus would have involved a number of senators. As praetor elect Priscus ventured to oppose Vitellius in the senate, and as praetor he maintained, in opposition to Vespasian, that the management of the finances ought to be left to the discretion of the senate. He proposed that the Temple of Jupiter Best and Greatest, which had been destroyed towards the end of the Year of Four Emperors, should be restored at the public expense. Lastly, Priscus saluted Vespasian by his private name, and did not recognize him as emperor in his praetorian edicts. At length he was banished a second time, and shortly afterwards was executed by Vespasian's order. His life, in the form of a warm panegyric, written at his widow's request by Herennius Senecio, caused its author's death in the reign of Domitian.
Family
Helvidius Priscus is known to have two children by Fannia: a son, Helvidius Priscus, later suffect consul, who was banished and likely executed by Domitian; and a daughter, Helvidia, who married Marcus Annius Herennius Pollio.. He probably also had a granddaughter, Helvidia Priscilla, who married Lucius Vipstanus Poplicola Messalla. Through her, he has known descendants into at least the 6th century.
James Madison wrote under the pseudonym Helvidius in 1793, in response to Alexander Hamilton's Pacificus columns on American neutrality in the French Revolutionary Wars.
