With President Obama and Republican leaders calling for cutting the budget by trillions over the next 10 years, it is worth asking how we got here — from healthy surpluses at the end of the Clinton era, and the promise of future surpluses, to nine straight years of deficits, including the $1.3 trillion shortfall in 2010. The answer is largely the Bush-era tax cuts, war spending in Iraq and Afghanistan, and recessions.

Despite what antigovernment conservatives say, non-

defense discretionary spending on areas like foreign aid, education and food safety was not a driving factor in creating the deficits. In fact, such spending, accounting for only 15 percent of the budget, has been basically flat as a share of the economy for decades. Cutting it simply will not fill the deficit hole.

The first graph shows the difference between budget projections and budget reality. In 2001, President George W. Bush inherited a surplus, with projections by the Congressional Budget Office for ever-increasing surpluses, assuming continuation of the good economy and President Bill Clinton’s policies. But every year starting in 2002, the budget fell into deficit. In January 2009, just before President Obama took office, the budget office projected a $1.2 trillion deficit for 2009 and deficits in subsequent years, based on continuing Mr. Bush’s policies and the effects of recession. Mr. Obama’s policies in 2009 and 2010, including the stimulus package, added to the deficits in those years but are largely temporary.

The second graph shows that under Mr. Bush, tax cuts and war spending were the biggest policy drivers of the swing from projected surpluses to deficits from 2002 to 2009. Budget estimates that didn’t foresee the recessions in 2001 and in 2008 and 2009 also contributed to deficits. Mr. Obama’s policies, taken out to 2017, add to deficits, but not by nearly as much.