Reihan Salam summarizes Charles Blahous

Roughly 49% of the fiscal deterioration relative to the expectations of the CBO circa its 2001 projections can be attributed to increased spending, 27% to the failure to predict the less-than-smooth business cycle perturbations of the decade, and 24% to tax cuts.

Here is more.  I have not myself worked through this calculation, but if you know of any good rebuttal to it, I will be happy to take a closer look and report back.  I believe it also does not include increases in state and local spending, which ultimately do tie back into the consolidated fiscal position of all U.S. governments as a whole.