The Story of Philosophy, by Will Durant, contains a section on Baruch Spinoza, including a bit on his Tractatus Politicus, wherein he speaks about democracy.

Democracy is the most reasonable form of government; for in it ‘every one submits to the control of authority over his actions, but not over his judgment and reason.’

The defect of democracy is its tendency to put mediocrity into power; and there is no way of avoiding this except by limiting office to men of ‘trained skill’. Numbers by themselves cannot produce wisdom and may give the best favors of office to the grossest flatterers. The fickle disposition of the multitude almost reduces those who have experience of it to despair, for it is governed solely by emotion, and not by reason.

Thus democratic government becomes a process of brief-lived demagogues, and men of worth are loath to enter lists where they must be judged and rated by their inferiors. Sooner or later the more capable men rebel against such a system, though they be of a minority. Hence democracies change into aristocracies, and these at length into monarchies ; people at last prefer tyranny to chaos.  

Equality of power is an unstable condition; men are by nature unequal and he who seeks equality among unequals seeks an absurdity.