Because front-running GOP presidential candidate Mitt Romney keeps harping on President Obama's deficit spending, Washington Post columnist Ezra Klein teamed up recently with some folks at the Center on Budget and Policy Priorities to calculate which recent president's policies have led to the largest growth in the national debt. George W. Bush was the winner. And not by a nose.

From 2001 to 2009, Bush's policies, including two wars, higher Pentagon spending in addition to those wars, tax cuts, higher discretionary spending and the prescription drug program contributed $5.1 trillion to the nation's debt. From 2009 to 2017 (using projections for 2011-2017), Obama's policies have added or will add $983 billion. Not even in the same ballpark. Klein:

There is a way to tally the effects Obama has had on the deficit. Look at every piece of legislation he has signed into law. Every time Congress passes a bill, either the Congressional Budget Office or the Joint Committee on Taxation estimates the effect it will have on the budget over the next 10 years. And then they continue to estimate changes to those bills. If you know how to read their numbers, you can come up with an estimate that zeros in on the laws Obama has had a hand in. [...] So the center built a baseline that includes everything that predated Obama and everything we knew about the path of the economy and the actual trajectory of spending through August 2011. Deviations from the baseline represent decisions made by the Obama administration. Then we measured the projected cost of Obama’s policies.

Here are the calculations:

For Bush: $1.812 trillion from the "Bush tax cuts"; $853 billion from the wars in Iraq and Afghanistan; $616 in higher Pentagon spending outside those wars; $608 billion in non-defense discretionary spending; $480 billion in "other tax"-related matters; $293 billion in entitlement changes; $224 billion in spending for Trouble Assets Relief Program (TARP) and the Housing and Economic Recovery Act; and $180 billion for the prescription drug bill.

For Obama: $874 billion for the American Reinvestment and Recovery Act (the stimulus package); $620 billion for the two-year extension of the Bush tax cuts; $324 in "other mandatory spending"; and $113 billion in "other revenue." Subtotal: $1.931 trillion. Subtracted from that are policies that reduce the net deficit: $502 billion in automatic spending cuts; $271 reduction in defense spending; $123 billion in reduced health care spending; $51 billion in reduced non-defense discretionary spending. Total: $983 billion.

There are all kinds of complications in this kind of calculation. It can be argued, for one thing, that we have a good handle, three years after Bush left office, on how big a debt pile his deficit spending ended up being. But, with Obama, we've only got three years of actual results and five years of "projection," which, in layperson's terms, amounts to "educated speculation."

Klein offers some other caveats, too. It is taken as a given by far too many in our national economic conversation, that "all deficit spending is equal and all of it is bad." That is completely wrong, and the austerity measures that the British government has imposed and the budget balancing of the Roosevelt administration in 1937 provide a perfect examples of why it's wrong: It can make economic downturns worse and cripple recoveries already under way.

In Keynesian terms, the better solution is to increase demand by stimulating the economy in recession, even if you have to borrow big do it. In good times, you pay off what you have borrowed and store up a surplus against the bad times. Modern Monetary Theorists challenge—from the left—the efficacy of the Keynesian approach in today's economy. But that's a long discussion for another time. What President Bush did pleased neither.

Eleven Februarys ago, in his first major speech to Congress, Bush vowed that the entire national debt would be paid off by ... well, by right now. Not quite what happened. Indeed, what did happen on Bush's watch is somewhat reminiscent of what took place under another fellow who made big talk about reducing the national debt: Ronald Reagan.

He came into office talking about how the not-quite-yet $1 trillion in national debt at the time would make a stack of $1,000 bills 67 miles high. Like so much else, he got that wrong; at four inches per million, it would only be 63 miles high. At any rate, by the time he left office eight years later, the debt had nearly tripled, to $2.7 trillion, and his metaphorical stack of $1,000s had soared 164 miles high. During Bush's eight years, based on Klein's and the CBPP's calculations, another 321 miles were added to the stack.

So next time Mitt Romney mouths off about the national debt and one of your TGIF or Facebook friends declares that the guy has a point, you might remind her exactly who was in office when most of that debt was accumulated.