One of the biggest criticisms of the newly proposed plan of government is that it violates the political belief that the legislative, executive and judicial and judicial branches should be separate and distinct. That there is too much mixing of powers in the U.S. Constitution and this threatens to progress to single body holding all the powers and trampling on the rights of the individuals.
The great authority on the division of powers is Montesquieu who held the highest regard for the British Constitution in which the branches had many interconnections. The threat, as articulated by Montesquieu, exists when the whole power of one branch is exercised by the same body that exercises the whole power of another branch. This did not occur in the British Constitution and has not been placed into the U.S. Constitution.
Each of the state constitutions as well, establishes a division of power that is not totally distinct and separate. There is not a single instance in which each branch has been kept totally separate. New Hampshire's constitution supports the idea that too much mixture is not good, but that some mixture is necessary. Therefore, the separation of powers described by the U.S. Constitution does not violate the principle of free government as it has ever been understood in America.
However, in a government of mixed powers, it is essential that each branch have a degree of control over the others. Most American constitutions have thought it enough protection to simply divide the duties amongst the different branches, but the experience of both Virginia and Pennsylvania provide evidence that dividing duties between branches does not protect each branch from the power of the others. The written demarcation of powers is not enough to prevent the concentration of powers in the hands of one body.
Some have argued that the people should be the final judge when one branch attempts to usurp the power of another, but there are many reasons why this would be dangerous to the government itself. Every appeal to the people to right the wrongs of government implies a defect in that government and reduces the respect the people give to that government. There is great danger in disturbing the public peace by frequently appealing to the public opinion. Finally, an appeal to the people would probably not adjust the imbalance that occurred in the first place.
In a representative republic, the most powerful branch is the legislative. The branches most likely to appeal to the people for usurpation of their powers would therefore be the executive or the judicial. The supporters of the executive and judicial branches be outnumbered by the supporters of the legislative branch, which is by its nature closer in proximity and affections with the people. Theoretically, the legislative branch represents the people's opinions. It is like asking the legislative branch to decide whether the legislative branch has usurped too much power.