The position was retained during the Republic when both consuls were unable to assume their duties, especially holding elections.
They were exclusively chosen from among patrician senators, and during the Conflict of the Orders, their appointment was sometimes designed to hinder plebeians from reaching power or passing laws.
The office of interrex was supposedly created following the death of Rome's first king Romulus, and thus its origin is obscured by legend.
The comitia to elect the first consuls were held by Spurius Lucretius Tricipitinus either as interrex or as praefectus urbi.
After that no interrex was appointed until the Senate, by command of Sulla, named L. Valerius Flaccus to hold the comitia for his election as Dictator in 82 BC.
In 55 BC, another interrex was appointed to hold the comitia in which Pompey and Crassus were elected consuls.
There were multiple interreges in 53 and 52 BC, the last known being Marcus Aemilius Lepidus (triumvir);[7][8] in 52 an interrex held the comitia in which Pompey was appointed sole consul.
Sulpicius Camerinus L. Valerius Potitus III M. Fabius Ambustus I & II Cn.