In a new reading of Tacitus's account of the quarrel between Helvidius Priscus and Eprius Marcellus at Hist . 4.6.3–4.10.1, I show that the historian stages a confrontation between panegyrical and Realpolitik rhetoric about the Principate. Helvidius uses the consensus-rhetoric of panegyric to propose that the senate claim the freedom they theoretically possess in the regime of a civilis princeps . Eprius describes the autocratic “reality” of the Principate in terms of contingency, necessity, and power. Helvidius's panegyrical fantasy runs up against practical limits, but Eprius's hardheaded truisms prove equally problematic for senatorial oratory. The failures of both speeches comment on the necessity of a consciously fictive “public transcript” such as Pliny's Panegyric while pointing to historiography as the proper place for Realpolitik truths. The debate sheds new light on Tacitus's praise of Trajan and Nerva at the beginning of the Histories as a locus for collective senatorial self-fashioning.