ModeledBehavior has an intriguing post comparing our current red/blue political polarization to the Byzantine Roman Chariot Racing Clubs, which gained political, military and social influence as the public rallied and politicians allied to Blue or Green.
The Blue-Green rivalry often erupted into gang warfare, and street violence had been on the rise in the reign of Justin I, who took measures to restore order, when the gangs murdered a citizen in the Hagia Sophia.[64] Riots culminated in the Nika riots of 532 AD during the reign of Justinian, which began when the two main factions united and attempted unsuccessfully to overthrow the emperor.
The wikipedia article on the Nika riots (linked in the quote above) is worth a read; very interesting.