By 23 BC, some of the un-Republican implications were becoming apparent concerning the settlement of 27 BC. Augustus's retention of an annual consulate drew attention to his "de facto" dominance over the Roman political system, and cut in half the opportunities for others to achieve what was still nominally the preeminent position in the Roman state. Further, he was causing political problems by desiring to have his nephew Marcus Claudius Marcellus follow in his footsteps and eventually assume the Principate in his turn, alienating his three greatest supporters – Agrippa, Maecenas, and Livia. He appointed noted Republican Calpurnius Piso (who had fought against Julius Caesar and supported Cassius and Brutus) as co-consul in 23 BC, after his choice Aulus Terentius Varro Murena died unexpectedly.