At the same time as Rome was experiencing victory and defeat abroad, it was becoming an increasingly violent society at home. Rome had been marred by political violence for decades, but something had inherently changed. Violence, rather than being a shocking aberration, had become the political process. It was normal. Moreover, it was not simply directed at or carried out by political elites and generals. Unlike the murder of Tiberius Gracchus by a senatorial mob or the civil war of Marius and Sulla with organized armies, Roman citizens were now clashing with Roman citizens in the streets of Rome.

Violence in Rome became prevalent through organized political gangs. The Roman people had long been members of various organizations called collegia. Some collegia were based on geography, some were for workers of certain guilds or trades, and others seem to have been simply social clubs; frequently they had a religious cult associated with them. As Rome became more volatile politically, many collegia became vehicles for organizing political gangs. For this reason they were all abolished in 64 BCE, save the most respectable and venerable, but in 58 BCE, the radical tribune Publius Clodius repealed the law of 64 BCE thereby allowing the collegia to operate as political gangs once more. Of course, the revival of the collegia was self-serving legislation, since Clodius promptly organized collegia that he would use to intimidate voters, threaten political enemies, and rough up the opposition.

The opposition did not tolerate this for long. They had their own money and political connections that could be used to form political gangs of their own. Pompey, who had become an object of Clodius's venom, saw to the creation of a rival gang, led by Titus Annius Milo, who was as ruthless as Clodius even if of a different political persuasion. In the forum and assemblies, the rival gangs of Clodius and Milo would go at each other or target those suspected of aiding the other side. Since Rome had no official police force, there was little that could be done to restrain these gangs once they had been legalized, short of bringing soldiers into the city to restore order, a prospect few wanted. The result was that for the better part of the 50s BCE, Rome would be at the mercy of violent political gangs.