Republics have a longer life and enjoy better fortune than principalities, because they can profit by their greater internal diversity. They are the better able to meet emergencies.
Public opinion is presumptively an input to policy formation in a democracy because politicians respond to it or at least are believed to respond [to it].
Where some people are very wealthy and others have nothing, the result will be either extreme democracy or absolute oligarchy, or despotism will come from either of those excesses.