When the Constitution was written, three fundamental units of the federal government were created. Each was intended to be as powerful as each other, regulating the others and being regulated by them simultaneously. We all know these three branches: the legislative branch, the executive branch, and the judicial branch.
The goal was to create three competing groups, each of which would try to hoard power, and in doing so, deny power to the others. And because each would be filled with the nation’s best and brightest, the constant competition would prevent any one branch from ever becoming too dominant. The goal, in effect, was the separation of power.
The separation of power restricts the ability of any one branch to become too dominant in the policy making and legislation writing process. Take for example the case of a generic law.
Only Congress can draft it and pass it, but both other branches can prevent its enactment. The President can veto it if he disapproves of it, and the courts can find it unconstitutional.
But neither the President nor the courts can be too radical in preventing the enactment of bills – after all, the Congress can impeach the President as well as any member of the federal courts, if they can summon up a large enough majority of Congressmen.
But if the Congressmen stray too far afield in their impeachment policies they, too, will find themselves out of a job when, in November, the voters remove them from office.
The coequal and competing powers are, ultimately, answerable to the public, and the constant competition keeps them honest. None can function without public approval, and because no person may be a member of any two (or god forbid, three) branches of government at once, it is impossible for any individual to gain too much power in the US government.
Some argue that in recent years, the separation of powers has been threatened by the increasingly powerful executive branch. Presidents now wield more power, both politically and legally, than ever before in the nation’s history.
But this is, in all likelihood, not an increase in power that has come at the expense of the legislative or judicial branches, but instead an increase in the total power of government, that has found its way principally into the hands of the executive branch, while the power of the legislative and judicial branches has remained constant.