Roman government in the early Republic was dominated by patricians, a wealthy, landowning minority who traced their ancestry to Rome's foundation, and had overthrown its monarchy. They shared the former powers of the kings among themselves, in the form of annually elected magistracies, senior military posts, and influential priesthoods. Republican government was headed by two consuls, advised by a senate of magistrates and ex-magistrates. Social class and status determined a citizen's voting rights, the value of his vote, and his lawful capacity for high civil, military and religious office; a patrician's vote far outweighed that of a citizen-commoner (pleb); this led to conflicts between the patrician minority and the far more numerous plebs. A series of constitutional reforms recognised wealthy, leading plebeian families as a legitimate aristocracy, and their most distinguished, reputable men as eligible for the highest elected offices.
Republican tradition and morality fostered competition for office and personal honours in service of the Republic. Among the elite, military service was a prerequisite to a career in politics. Patronage was an essential feature of Rome's economy and social structure. Republican conservatives and traditionalists were wary of demagogues; appeals to the plebs for direct political support could be interpreted as tyranny, and subversion of established order. The aristocratic Gracchi brothers introduced land reforms on behalf of landless plebs, and were murdered by their opponents.
During the first two centuries of its existence, the Roman Republic expanded through a combination of conquest and alliance, from central Italy to the entire Italian peninsula. By the following century, it included North Africa, most of the Iberian Peninsula, and what is now southern France. Two centuries after that, towards the end of the 1st century BC, it included the rest of modern France, Greece, and much of the eastern Mediterranean. Factional tensions led to a series of civil wars, leading to Julius Caesar's crossing of the Rubicon River, his appointment as dictator for life and assassination in 44, the defeat of Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the Senate's grant of extraordinary powers to Octavian as Augustus in 27 BC, effectively making him the first Roman emperor and ending the Republic.
Roman monarchs had been elected for life by the patrician noblemen who made up the Roman Senate. The last Roman king was Lucius Tarquinius Superbus ("Tarquin the Proud"). In the traditional histories, Tarquin was expelled in 509 BC because his son, Sextus Tarquinius, had raped the noblewoman Lucretia, who afterwards took her own life. Lucretia's father, her husband Lucius Tarquinius Collatinus, and Tarquin's own nephew, Lucius Junius Brutus, mustered support from the Senate and army, and forced Tarquin into exile in Etruria.
The Senate agreed to abolish kingship and transferred most of the king's former functions to two consuls, who were elected to office for a term of one year. Each consul had the capacity to act as a check on his colleague, if necessary through the same power of veto that the kings had held. If a consul abused his powers in office, he could be prosecuted when his term expired. Brutus and Collatinus became Republican Rome's first consuls. Despite Collatinus' role in the creation of the Republic, he belonged to the same family as the former king, and was forced to abdicate his office and leave Rome. He was replaced as co-consul by Publius Valerius Publicola.