Answer:
First, one has to be clear about what we are talking about. In a pure democracy, the people simply decide together what they are going to do. The rule of law matters a little but not terribly much in that situation since if there are any disagreements about what we all agreed to, we simply get back together and decide again. In practice, of course, a pure democracy does not work for anything more than a very small group.
What we generally mean is a representative democracy, or a republic. This means that there are certain people elevated to positions of authority and decision-making for society (temporarily) based on democratic selection. What makes their power temporary? What ensures that they only exercise the power they are supposed to? What prevents any of these people from becoming dictators? We may want to say that they only have the powers that we grant them democratically but ultimately those individuals in power are the ones that control the process. Democracy at a large scale, even with respect to just elections, only works if there are established procedures that are strictly followed. The principle of the rule of law means that at the most basic level we all agree that the laws as written down are what “rule” everything and everybody. Nobody can change that fact. So if some individual chooses to say they have some god-like authority, our society as a whole will not follow them because we all agree the Constitution supersedes their opinion about any authority they believe they should have. It is a fundamental social contract that we all share that makes our laws work and makes it theoretically impossible for somebody to become a dictator. Without this implicit social contract, the Constitution and the laws mean nothing.
NOTE: We tend to associate other ideas like “equality before the law”, “civil rights”, and other ideals with the rule of law. While the rule of law can help enable these things, they are not the same thing nor are they specifically part of the rule of law. The rule of law can allow and even enable inequality before the law (as it did in the Roman Empire) and a variety of other things we consider wrong. In fact the rule of law does not even have anything to do with democracy at all. It is simply a principle that allows a stable, functioning society by establishing that we all have to live by the agreed-upon standards. But as stated, a representative democracy cannot function without it.
Explanation: