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The history of Rome can be divided into three time periods: the Roman Kingdom (753 BCE-509 BCE), the Roman Republic (509 BCE-27 BCE), and the Roman Empire (27 BCE-476 AD). Throughout the existence of the Roman government until its fall, one fundamentally traditional aspect of Roman politics was the fact that it was a Republican government, even when it was a monarchy. Even while it was an empire, the Roman government still maintained some aspects of a democratic republic though all real power of course rested in the hands of the emperor. Regardless of the Roman government's democratic republican aspects throughout all three periods, the Roman government was never a traditional democratic Republic because the power always rested in the hands of the aristocracy.
During the days of the Roman Kingdom, the kings were not chosen through family lines as with traditional monarchies; instead, the kings were democratically elected. Like monarchs or dictators, however, the kings did reign until their deaths, and all power rested in the kings' hands. After the death of a king, the Roman Senate was responsible for nominating a new king. To do so, the senate would first choose one of its own members, called an interrex, to look for a king to nominate over a 5-day period. If a king had still not been nominated after that 5-day period, another interrex would be chosen, and that cycle would continue until an interrex found who he thought was an appropriate candidate to nominate as king. Once the senate approved the interrex's nomination, a Curiate Assembly was held over which the interrex would preside ("Roman Kingdom: Election of the Kings"). A member from each Curia formed the Curiate Assembly. When Rome was a kingdom, its people were divided up into groupings called Curia based on Rome's families. Each member of a family belonged to the same Curia, and there were 30 Curia in all. All members of each Curia would first vote on the king nominated, and the majority vote of each Curia would decide how that particular Curia would vote on the nomination. One member from each Curia would meet for the Curiate Assembly and vote on the nomination ("Legislative Assemblies of the Roman Kingdom: Curiate Assembly").
In 510 BCE, the Roman nobles revolted against Etruscan King Tarquiniu Superbus, a revolt that led to the birth of the Roman Republic. In the early days of the Republic, the senate still possessed little power. In fact, the senate chose two consuls to hold power for one year and then switch, much like joint kings. The senate passed all power to the consuls and acted as advisers, just like it did under the king. As time progressed, the senate obtained more power until it had authority to make law-making decisions ("Roman Republic: Senate of the Roman Republic").
In 44 BC, Augustus Octavius joined forces with Mark Antony and Marcus Lepidus to defeat Julius Caesar's assassins in civil war at Philippi, but by 27 BC, the three turned against each other and incited the Roman Republic to a second civil war. Augustus Octavius was the winner of the second civil war and was declared imperator, meaning commander, by both the Roman Senate and the People of Rome ("History of the Roman Empire"). Even during the days of the Roman Empire, the Roman Senate still remained in position; however, once again, the senate lacked power, just like it did during the days of the Roman Kingdom. The senate even lacked the power to elect the next ruler as it did in the days of both the kingdom and the Republic; instead, each emperor chose his own successor out of his family line. Some duties the senate did retain were the abilities to administer the foreign embassies, pass decrees, serve as the highest court, and elect magistrates though the emperor had the final say concerning the election of magistrates ("Roman Empire: Government Structure"; "Roman Senate: Senate of the Roman Empire").