This question came up in a class on Democracy and its problems around the world.
In every democratic country where a powerful executive branch has been established, that president has eventually subsumed almost total power, with one exception, that being the US. But we questioned if that was true of the US.
more below the Jump
Call it, if you will,
el presidente syndrome. First really seen in the Latin-American 'Banana Republics' of the late 19th and the 20th century, as well as the various 'Presidents' in the republics of the Former Soviet Union, and the kleptocratic regimes in central Africa. Even the Roman Republic fell under the control of its Consuls.
The problem is that Presidencies accumilate power like a snowball. If there is a national crisis, the Presidency requests and usually gets extra power to deal with the crisis. What happens though, is that power almost never receeds from the Presidency afterward:
The first real jump in Presidential power came in the Civil War. Lincoln dominates the politics of his presidency in ways the senate-dominated politics of the first half of the 19th century did: Henry Clay and Daniel Webster were Senators, and they made the long reaching decisions of their time. Licoln, however, exerted power over the congress because of the national emergency.
That power never quite returned to Congress. It wasn't exercised much, but it was there.
The next major ratcheting might very well be Teddy Roosevelt and his ability to carry out a form of American Imperialism at a time when all great powers did so.
After that, the next major ratchet in power is the Great Depression and WWII. These crises elevated FDR to a Cult of Personality that rivaled that of Stalin. Roosevelt was elected four times, and had he not died, likely could have been elected for at least another generation if he wanted.
The Cold War had Congress funnel still more power to the Presidency, one reason we haven't declared war on anyone since 1941, inspite of at least ten military actions that could have been called 'wars' since then (Not only Korea, Vietnam, and Iraq, but smaller actions like Kosovo, Bosnia, and Grenada).
One complaint brought up in the class was that our version of Democracy can suffer from 'divided government' in which opposing parties control congress and the presidency, leading to gridlock and little getting done.
We pointed out that the opposite problem is one we face now: A Congress of the same party basically funnelling power to the like-party executive, abrogating its own responsibility.
We had to conclude that Parliamentary-style democracy may end up being a better long term choice. This effect can and does happen with both parties: a Democratic Congress funnelld power to Franklin Roosevelt that was, for its time, just as unprecedented as this congress abrogating its oversight responsibilities.