Institutions such as the consuls, the senate, and tribunes evolved significantly in the early republic but remained relatively stable from the fourth century BC.
[23] Votes were never called on the market days on which rural citizens might be present in the city; arcane and time-consuming procedures persisted unchanged.
The first, the comitia (or comitiatus), was an assembly of all Roman citizens convened to take a legal action, such as enacting laws, electing magistrates, and trying judicial cases.
[38] In the middle republic, only a few bills (most famously, war with Macedon in 200 BC, which was passed when the centuries were recanvassed shortly thereafter) were rejected, mostly due to counter-mobilisation from other politicians.
[40] The curiate assembly (Latin: comitia curiata) traditionally dates to the early monarchy, from 30 divisions of the city made by Romulus.
This assembly had authority over some elements of family law and ratified the imperium of elected magistrates and promagistrates through a lex curiata de imperio.
[43] By the middle republic, the connection between voting power and military service had long ceased, turning into a system to massively overweight older and richer citizens.
[51] The vast majority of legislation was enacted in the comitia tributa,[43] which also elected quaestors, curule aediles, military tribunes,[52] and other minor magistrates.
[55] However, other scholars counter that late republican practice shows that curule magistrates held elections and legislated before the tribes, implying it could not be a solely plebeian institution.
[62] Some of its responsibilities were enshrined in specific legislation, such as the lex Caecilia Didia which gave the senate power to declare a law invalid.
[67] In line with the censor's duty to protect morals, senators could be expelled if they were not of good character, found guilty of a criminal offence, or tainted with infamia.
[79] In such instances, the consul presented information to support his position that the republic was in imminent danger and the senate responded with an opinion that "magistrates [should] defend the res publica and take whatever measures they thought necessary to see that the state did not suffer any harm": the effect of a decree from a legal perspective was minimal and it granted no legal immunity;[80] it rather granted political cover, along with the promise of later senatorial sanction, for magistrates to evade accountability for illegal actions by giving the senate's support for them.
[51] The two consuls were the supreme magistrate for an annual term, endowed with imperium to command both in the civic and military spheres, and the auspices allowing them to consult the gods for the people.
[86] They were the normal military commanders during the late republic, with the two consuls leading separate consular armies in war, where their powers were largely unlimited.
In domestic affairs they were responsible for holding the annual feriae Latinae (a spring festival), receiving embassies from foreign states, conducting discussion on those matters in the senate, and proposing legislation.
[88][89] Also endowed with imperium, they were initially elected to military commanders – possibly to defend Rome while the consuls attacked – and as governors of provinces; only later would their main responsibility become to administer justice.
[91] Over time, as Rome's empire grew, the two annual consuls and the limited number of praetors ceased to be enough to command its many armies in the field or administer its many provinces.
[112] In the middle and later Republic, with the office of dictator falling out of fashion, the need for dictatorial authority was not granted to some extraordinary magistrate, but rather, to the consuls, through a senatus consultum ultimum, or final decree.
[118] Many modern scholars now view, however, the Livian and annalistic accounts to be a "literary creation of the late republic"[119] and that they broadly "cannot retain much value for... reconstructing early Roman history".
With the pressure of an external threat, the patricians were forced to recognise the office of plebeian tribune (Latin: tribunus plebis) and accept their sacrosanctity.
[133] The ancient literary sources also report the regular election of consular tribunes as a reaction of increased demand for generalship or as means to prevent plebeian assumption of military leadership; some modern scholars, however, reject these explanations and suggest them to be a late republican misunderstanding of the evidence.
[135] This date also marks the emergence of the classical form of the republic with the end of the consular tribunate (if it existed) and the creation of the praetorship and aedilate.
[137] The consulship and praetorship were at this time not clearly separated: "scholars increasingly view the Sextian-Licinian Rogations as establishing a college of three (and only three) praetors, two of whom eventually developed into the historical consuls".
A plethora of such tools developed, including laws making certain practices illegal, such as extortion, as well as establishing quaestiones perpetuae to try them for violations.
[146] However, the senate's institutionalised resorts to force augured poorly for the republic, setting a precedent to resolve disputes between citizens not by consensus and arbitration but rather by the elimination of enemies from the body politic.
[147] The Sullan civil war, proscriptions, and reforms that followed saw a change in the character of the res publica, producing a novel constitutional structure unlike the consensus-based senatorial culture of the middle republic.
[152] With little legitimacy, his regime faced continuation of the civil war with Quintus Sertorius as well as a revolt in 78 BC by the then-consul Marcus Aemilius Lepidus.
[153] The larger senate and the retention of more imperium-holding magistrates close to the city made politics dysfunctional, difficult to influence, and unpredictable.
[158] Moreover, senatorial sanction for special commands was common throughout, with Caesar's Transalpine Gaul assigned by the senate and Pompey's commissions for corn and renewal in Spain also emerging therefrom.
[166][167] The transformation away from the republic would only emerge with Augustan settlements and the emperor Tiberius' successful accession in AD 14, placing Rome on a path away from a state without the domination of a single man.