The Roman Republic was built from a curious mixture of piety and superstition, civic pride and vindictiveness, virtue and greed. Embedded in the Roman psyche was a fierce hatred of tyranny, preserved in the Roman collective memory in tales of the arrogance and cruelty of Rome's last monarch. Hundreds of years after the revolution that drove Tarquinius Superbus from their proud city, no title aroused Roman wrath more fearfully than that of "king."
Romans established a form of government based on the election of leaders by a free citizenry, diffuse power, a complex system of checks and balances, and strict term limits to guard against tyranny. Though the Roman Republic gave most power to the noble classes (or Patricians), over the years the common people (or Plebians) successfully demanded more and more rights and were able to force concessions, including the appointment of a Tribune elected by the commoners, who had the power to veto any laws promulgated by the consuls or the senate.
The spread of Roman power created a dilemma for the Republic. On the one hand, the conquest of distant lands brought prosperity and security to Rome, and seemed to be in the best interests of the people. On the other hand, it created peculiar burdens related to governing and administering lands and peoples quite alien to Rome. The Republican form of government was ill-suited to the task, and the occupation of foreign lands created a unique set of dangers. One constant threat was the temptation, seemingly irresistible to Roman governors, of exploiting their unchecked power over non-Roman subjects for personal gain. Time and time again, the Republic found itself dispatching legions to the "provinces" to quell rebellions caused by the malfeasance of the men who should have been maintaining order and security, but instead built personal fortunes by bleeding their subjects dry.
The rise of Rome created another, even more dire threat to republican government: the rise of a class of super wealthy. By the first century B.C., the Roman political scene was evolving into a struggle between titans, men like Marius and Sulla, Crassus, Pompey, and Caesar, who had amassed such vast personal wealth and power that they could afford to buy the allegiance of the Roman Senate and pull the levers of world power. Rising inequality rendered the plebian classes increasingly hungry and desperate, and introduced an even more dangerous element into the politics of the city: class warfare and mob violence.
The old order was incapable of dealing with these challenges. Individualistic notions of virtue made it impossible to conceive of putting limits on the informal power afforded by wealth. The Republic's relationship to its conquered provinces was shaped by xenophobia and chauvinism, and slavery, making it impossible to integrate the "empire" into the political order. Conquered peoples dreamt of mystical messiahs to rescue them from the great whore rising from beyond the waters, while the common people of Rome dreamt of revolution. The "great men" of Rome still thought only of ever more outrageous glory piled upon glory. And from this poisonous mixture, the Republic suffocated and the Empire was born.
The constitution of the Roman Republic did not unravel overnight. By the time defenders of the constitution like Cicero and Cato took a stand, it was far too late. There was already too much power in the hands of ambitious men, and years of class warfare had left the Republic without the resources to resist them. Cato's inflexibility against Caesar was the equivalent of cornering a tiger, and may have hastened the end. But the compromises of Cicero did not save the Republic either.