"Power tends to corrupt, and absolute power corrupts absolutely”. This famous dictum of Lord Acton is as relevant today as it was when stated in 1887. It applies to the private sector, such as private monopolies, as well as the public sector, but this insight has become much more important in the public sector since he wrote because of the large expansion of governmental powers during the past 70 years.
I would only add to Acton’s dictum that discretionary power is even more corrupting than the power embodied in regulations. The most dangerous trend in presidential power has been the growth in presidential willingness to take many discretionary actions that not only have little basis in law, but also frequently cause great harm to the economy and the society at large. The harm consists of both the direct damages from the actions, and the often large but indirect cost from the increased uncertainty and fear about the political environment faced by business, unions, and other groups.