Robert J. Samuelson, “The $12 Trillion Misunderstanding,” The Washington Post, July 27, 2012

In this keeper of a column, Bob Samuelson explained how the deficit got so bad:

Back in 2001, the Congressional Budget Office (CBO) projected federal budget surpluses of $5.6 trillion for 2002-11. Instead, we got $6.1 trillion of deficits — a swing of $11.7 trillion. Naturally, political recriminations followed. Who or what caused the change?
We now have evaluations from the CBO and two nonpartisan groups: the Committee for a Responsible Federal Budget (CRFB) and the Pew Fiscal Analysis Initiative. They all point in the same direction.”
For starters, a weak economy was the largest cause. The CBO attributes $3.2 trillion of the $11.7 trillion shift (about 27 percent) to “economic and technical changes.”
all of Bush’s 2001 and 2003 tax cuts — which, except for benefits for the rich, are now supported by Obama — had a bigger effect, accounting for about 13 percent of the debt swing.
Iraq and Afghanistan wars: 10 percent. Increases in discretionary domestic spending: 10 percent. Other increases in defense spending: 5 percent. Obama stimulus: 6 percent. 2010 tax cuts: 3 percent. Medicare drug benefit: 2 percent. Other tax cuts and means of financing: 12 percent. Higher interest costs on larger federal debt: 11 percent.