In 135 BC, a massive slave revolt occurred in Sicily. This was the first slave revolt on this scale in the history of Rome. The slaves across the island rose up and butchered their former masters. The revolt, however, did not go well. Once the slaves were in charge of the island, chaos ensued. They had no effective leadership with which to organize themselves. In 132 BC, the slave was at last put down. Over 20,000 of the starving slaves were crucified by the Romans.
Like much of Italy to the north, the island of Sicily had consisted predominately of patrician-owned large agricultural estates, which they had acquired through questionable means. These states were now virtually all worked by slaves, who had become far less expensive due to Rome's recent conquests. The landless farmers were forced to move to the cities, especially Rome, where they became part of the plebeian mob. Most became day-laborers, barely able to support themselves. They survived because of the inexpensive grain, sometimes even doled out to them, produced by the large agricultural estates where they had once worked.
It was in this time of unrest that patrician politicians first began in earnest to curry the favor of the landless poor by fighting for their rights. In 133 BC, Tiberius Gracchus, the grandson of Scipio Africanus, was elected to the office of tribune. This year, the territory of Pergamum was bequeathed to Rome in the will of its king, who had been an ally of the Romans. Tiberius proposed using the profits from this new territory to institute sweeping agrarian reforms.
Tiberius Gracchus proposed that the landless poor be given small estates, which would be divided up from Rome's public land. These new farms would be created by enforcing the law that limited the land that any man may possess to 500 acres per family member. Profits from Pergamum would be used to reimburse those who had lost land.
Tiberius argued to the wealthy landowners that his plan would reduce the danger of revolt by the mob, as well as boost the number of soldiers the Romans could field (soldiers were required at this time to be landowners). Though his arguments were valid and intentions good, the way Tiberius went about his reforms was treasonous.
Naturally, the senators would be against any reforms which might cost them some of their own land. Therefore, Tiberius decided to circumvent the Senate altogether. He instead used the plebeian assemblies to pass laws and his power of veto to bring the Roman government to a standstill. The senators, however, refused to bow to his demands. While Tiberius was running (illegally, since consecutive offices could not be held) as tribune a second time, a mob was formed by his cousin Scipio Nasica, which beat him to death in the forum.
His uncle, Scipio the Younger, had led the senators in their fight against Tiberius' reforms. He vehemently resented his nephew's attempts to subvert the traditional Roman political structure. In 129 BC, Scipio was found dead in his bed with signs of strangulation on his neck. So inflamed was the poor of Rome over the death of Tiberius that no investigation was made and Scipio was quietly buried.
The attempted reforms of Tiberius were now championed by his brother, Gaius Gracchus. In 123 BC, he was elected the position of tribune, just like his brother. Gaius, however, was far more successful than his brother by gaining the support of the equestrian class as well. Not only did he push through the Senate land reforms, but also public works projects and rights for the equestrians.
Eventually, however, Gaius became too progressive for many his own supporters to stomach. Mainly, he attempted to give Roman citizenship to all Italians. In 121 BC, Gaius failed to win reelection to his third term. He and his supporters began to riot. Seeing their oportunity, the Senate passed a senatus consultum, which effectively gave the consul the right to do whatever he thought best to preserve the republic. The consul, named Opimius, brought in several thousand soldiers and attacked the mob. Gaius, seeing his followers slaughtered, ordered a slave to kill him.
The reforms of the Gracchi brothers were short-lived and themselves did not have a great impact on Rome. What is important about them, however, is that they show the rise of the popular party in Rome. From the time of the Gracchi on, Roman politicians in the Republic were divided between the optimates and the populares. No longer was the Senate the overwhelmingly dominant power it once had been.