The Congressional Budget Office estimate says that if Obama's February budget submission were enacted into law it would produce deficits totaling $9.5 trillion - an average of almost $1 trillion a year.
Obama's budget foresaw deficits totaling $7.2 trillion over the same period.
The difference is chiefly because CBO has a less optimistic estimate of how much the government will take in from tax revenues, partly because the administration has rosier economic projections.
The Senate is also worried about the president's budget numbers.
This exchange between Jeff Sessions, the Republican Senator from Alabama, and Heather Higginbottom, the new nominee for Deputy Director of OMB, is from Higginbottom's confirmation hearing, which took place yesterday. Sessions grills Higginbottom about Obama's budget, and boy is it painful to watch (h/t Hot Air).