It does not take much probity for a monarchical or despotic government to maintain or sustain itself. The force of the laws in the first, and the ever-threatening arm of the prince in the second, determine or contain everything. But a popular state needs to be driven by something more, which is VIRTUE. 
What I say is confirmed by the whole body of history, and is perfectly consonant with the nature of things. For it is clear that in a monarchy, where the person who executes the laws holds himself above them, less virtue is required than in a popular government, where the person who executes the laws is aware that he himself is subject to them and that he will feel their weight.
It is clear that the monarch who, through bad counsel or negligence, ceases to see that the laws are executed can easily repair the damage : he has only to get a new counsellor, or correct his own negligence. But when, in a popular government, the laws have ceased to be executed, since this can result only from corruption of the republic, the state is already undone.
What a spectacle it was in the last century to witness the ineffectual attempts of the English to establish democracy for themselves ! As those who were involved in politics had no virtue, as their ambition was stimulated by the success of the one who had been the most daring,  and as the spirit of one faction was beaten back only by the spirit of another, the government was constantly changing ; the distraught people was seeking democracy and finding it nowhere. Finally, after many upheavals, reversals, and tremors, they had to settle on the very government they had banished.
When Sulla wanted to restore freedom to Rome, Rome could no longer accommodate it ; she had no more than a trace of virtue remaining ; and as she had less and less, instead of awakening after Cæsar, Tiberius, Caius,  Claudius, Nero, and Dometian, she was ever more enslaved ; all the blows fell on the tyrants, and none on tyranny.
The Greek political writers who were living under popular government recognized no force that could sustain them other than virtue. Those of today speak to us of nothing but manufacturing, trade, finance, wealth, and even luxury.
When that virtue ceases, ambition enters the hearts that can receive it, and avarice enters them all. The objects of desire change : what they loved, they love no longer ; they were free with the laws, and now wanted to be free against the laws ; every citizen is like a slave who has escaped from his master’s house ; what was a maxim is now called rigidity ; what was a rule is called constraint ; what was attention is called fear. Frugality is now their avarice, and not the desire of acquiring. Formerly the property of individuals constituted the public treasury, but now the public treasury becomes the patrimony of individuals. The republic is a carcass, and its strength is no more than the power of a few citizens and the license of all.
Athens encompassed the same forces while it dominated with such glory and while it served with such ignominy. She had twenty thousand citizens  when she defended the Greeks against the Persians, rivaled Lacedæmon for hegemony, and attacked Sicily. She had twenty thousand when Demetrius of Phalerum counted them  the way slaves are counted in a market. When Philip dared to prevail in Greece, when he appeared at the gates of Athens,  she still had lost nothing but time. We can see in Demosthenes what pains it took to awaken her : Philip was feared there as the enemy not of freedom, but of pleasures.  That city, which had overcome so many defeats, which returned to life after its destructions, was conquered once and for all at Chæronea.  What does it matter if Philip sends all the prisoners home ? He is not sending men. It was still as easy to overcome the Athenian forces as it would have been difficult to overcome her virtue.
How could Carthage have managed to sustain itself ? When Hannibal, as prætor, wanted to prevent the magistrates from pillaging the republic, did they not go and accuse him before the Romans ? These wretches wanted to be citizens in the absence of a state, and owe their wealth to the hands of their destroyers ! Rome soon demanded three hundred of their principal citizens as hostages ; she made them turn over their weapons and vessels, and then declared war on them. By what despair wrought in a disarmed Carthage  we can gauge what she could have done with her virtue when she was at full strength ?