Much of the growth of presidential power has occurred due to?

Several reasons:

1) The increased responsibility of government causes a consequential increase in complexity. This has resulted in more departments to ensure that the government can effectively keep up. The growth of the overall executive branch significantly increases the influence of the President.

2) The executive branch controls intelligence gathering agencies such as the CIA and the FBI, causing the President to have a more direct link to obtain and keep information than Congress. As they say, "knowledge is power," especially in the information age.

3) The increased control of federal administrative bureaucracy shown under both the Clinton and Bush administration causes an expansion in size (see point 1) and influence of the presidential position.

4) Constitutionally, the presidential position is very vague. In contrast to the Articles Congress must live by, the Presidential is ruled by a responsibility "to take care that the laws be faithfully executed" and have authority under the term "executive power."

5) As the ability to attack is no longer vested in soldiers marching, war has become a fast endeavor, causing the responsibility to respond to be entrusted in the quickest-acting branch--the executive, not the legislative.

6) The President can gain media attention more than any other one person and can easily affect and control the nation's political agenda.

There are several others, but these are some of the most significant.