This clear, concise video is a must see exploration of why the founding fathers established a constitutional republic and not a democracy, a topic that holds great significance in our troubled times:
Republic vs. Democracy
The United States of America is a Republic.
Our Founding Fathers wanted our country to be one that would last for generations to come. They knew the strength of a republic and that a country to last had to be one of the people not the government. John Adams has been cited as saying this about democracy: "Remember, democracy never lasts long. It soon wastes, exhausts and murders itself. There was never a democracy yet that did not commit suicide."
* * * * * * * * * * * * * * * * * * * * * * A republic is a form of government in which the head of state is not a monarch and the people (or at least a part of its people) have an impact on its government. The word 'republic' is derived from the Latin phrase res publica which can be translated as "public affairs".
Both modern and ancient republics vary widely in their ideology and composition. The most common definition of a republic is a state without a monarch. In republics such as the US and France the executive is legitimated both by a constitution and by popular suffrage. In the United States Founding Fathers like James Madison defined republic in terms of representative democracy as opposed to only having direct democracy, and this usage is still employed by many viewing themselves as "republicans". In modern political science, republicanism refers to a specific ideology that is based on civic virtue and is considered distinct from ideologies such as liberalism.
Most often a republic is a sovereign country, but there are also subnational entities that are referred to as republics. For instance the Soviet Union was composed of distinct Soviet Socialist Republics. *Article IV of the Constitution of the United States "guarantee[s] to every State in this Union a Republican form of Government."
Democracy is a principle that the control of authority comes from public, and ruler and non-ruler are the same. It is derived from the Greek demokratia, "popular government", which was coined from demos, "people" and kratos, "rule, strength" in the middle of the fifth-fourth century BC to denote the political systems then existing in some Greek city-states, notably Athens following a popular uprising in 508 BC. A democracy can denote either direct or indirect rule by the people.
In political theory, democracy describes a small number of related forms of government and also a political philosophy. Even though there is no specific, universally accepted definition of 'democracy', there are two principles that any definition of democracy includes. The first principle is that all citizens, not invested with the power to govern, have equal access to power and the second that all citizens enjoy legitimized freedoms and liberties. 
* * * * * * * * * * * * * * * * * * * * *It is important to note what Article IV of the Constitution of the United States guarantees to the states: every State in this Union a Republic form of Government.