When the founders created the United States of America they intentionally created the three branches. Do you know why? Did you just think that three sounded kool, or that maybe it has something to do with the Illuminati? It was all about reducing the power of government over the people. The Congress, this includes both the House and the Senate, was the most powerful arm of the government. They could raise taxes, declare wars, initiate tariffs, make immigration law, etc. There is a whole list of what the founders wanted them to be part of but there were some things they couldn't do. They can't FIGHT a war (no one can fight a war by committee), they can't negoiate treaties, they can't choose who shall be a judge (the Senate only consents to the choices of the President), and they can't ignore the consitutional liberties enumerated by the Constitution. The founder expected the Congress to carry the weight of government. The President was part figure head, part general (in case of war, break glass), and the face of the United States.
What was the point? The major result was to prevent a branch of government to becoming too radical or powerful over the other two branches. A Congress could declare a war but a President could refuse to act on such a declaration. Think of an election year and the sitting members of Congress want to stir up the people. They could declare war on some small country like Mexico (think 1840), send an expedition and end hostilities after the election. The President, who is ultimately responsible for the lives of the soldiers as commander in chief, could refuse to go along with the political "wag the dog". By the same action, a Congress could refuse to support a President who is doing the same thing. The Congress can make onerous laws but it is hoped that the Supreme Court would shoot them down for being unconstitutional. There was a time when the Supremes would look at a law, decide if it was constitutional, and just negate it. They didn't try to fix it. Unlike Obamacare, the Supremes did not try to craft law by finding some parts constitutional and rename other parts so that they were constitutional. Speaking of the Supremes, a President has the right to nominate anyone he (or she) chooses but the Senate has a responsibility to confirm or deny any of those choices that may be deemed too radical.
These separation of powers was supposed to promote a moderate, rational government of the represented and not lead to a radical government of the leadership. All three branches have failed in their historical roles and responsibilities which brings us to the silent partner; the people. Our government only governs with the CONSENT of the people. If government (or a party) steps outside of the role then the people have the right (according to Jefferson) and a responsibility (according to Madison) to dissolve the government or bring it back into line.
This is where we stand today.