The answer lies in the Constitution itself, a document which was written by men who understand what a government operating under tyranny itself could do and they strove to make sure it didn't happen in the new nation they were tasked with getting underway. After all, George Washington could have been crowned King, but he knew what that would ultimately lead to. And these men banded together, despite sometimes heated debate and disagreement, to hammer out a document which could do those things, provided that the land was inhabited by those who both understood what it meant and desired to remain free. Today, with so many who either don't know or don't care about such things, it becomes much more tenuous and it is incumbent on Americans to forge together a majority to maintain support and belief in that wonderful document.
Here's how the Constitution is constituted and what it should mean for the goings on of today. First, it is a document with separation of powers between three equally important components, yet in different ways. The President is the Chief Executive, responsible for the day to day functioning of the government while also serving as the principal representative of the land. The Congress, made up of the Senate and the House, writes the laws. The Senate also has the responsibility for ratifying treaties and for giving advice and consent in the appointments of importance to the President, the Cabinet and select others. Then, there's the Judiciary, the body tasked with interpreting the Constitution, not rewriting it and creating law.
The problem we have today is when some of the different components mentioned either fail to do their duties or they abrogate them to someone else. Take, for example, the Obama healthcare plan. It became law because Congress didn't apply due diligence, bickering instead and then the President took the law and allowed the bureaucracy to create complicated rules by which it would operate. It has been inoperative because it is not based upon reality, both in practice and in terms of economics.
Today, the Justice Department and its subordinate Federal Bureau of Investigation has seemingly placed itself above the law. Congress is asking for documents to show why and what they have done in secret and they have repeatedly turned them down. And remember, nothing in the Constitution created either bureaucratic body, they were authorized by the Congress to work for the President and assist him in carrying out his burdensome duties. But Congress, clearly in the Constitution and with the House holding responsibility for initiating appropriations, clearly has the authority to conduct oversight of both the DOJ and FBI.
The Judiciary has gone through a long history of expanding the rule of the federal government, largely originating from the Commerce Clause which would probably make Jefferson and Madison roll over if they knew what it was used for. In doing this, many of the prerogatives which were granted to the states have been negated, thereby reducing the authority they were originally granted. And when the election of Senators was taken away from the state legislatures, changed instead to a vote by the people, the representatives for the states were removed. Just think, had that not been the case, the likes of John McCain would have been working for the State of Arizona instead of who knows who. Then entire concept of Federalism was deal a major blow over time.
So, in a nutshell, if America is to fall from being a democratic republic to a Robispierre version of mob rule tyranny, it will do so because leaders are weak, they don't stand for the oath they agreed to and were sworn under and that allows mere men (or women) to be the rudder of the ship, instead of granting that power to the law. Whether it be through mob action, tyranny within the bureaucracy and political elites, or lobbyists and corporatists, it would be a disaster. We, the people, must not allow that to happen. We have the power, we just have to use it legally, with our brains and with the backing of our God. Are you ready?