Presidential administrations and the many Congresses as well. Here is an interesting article:

http://useconomy.about.com/od/usdebtanddeficit/p/US-Debt-by-President.htm

You will note they say that the debt increased 52% over the last 6 years, not doubled. They say it did double over the course of Bush's administration. No doubt it increased significantly during the the administrations of Bill Clinton and the first George Bush as well. It has increased under both parties and seems to be on an upward track no matter who is in charge.

It's obviously complicated and blaming it on one party over the other is not only demonstrably wrong, it's counterproductive to improving the situation.

Michael Siskin