HEMPSTEAD, N.Y. - During Tuesday night's debate here at Hofstra University, President Obama once again attacked Mitt Romney's proposals by saying "the math doesn't add up."

Obama has a point -- Romney will have difficulty balancing the budget by his second term while walling off roughly two-thirds of the budget from cuts, and cutting tax rates by 20 percent without touching popular deductions. But if Obama wants to be a stickler for math, that opens up his own tax and spending claims to more scrutiny. In reality, it is mathematically impossible to protect popular programs like Medicare, Medicaid and Social Security from serious cuts and avoid massive deficits merely by raising taxes on the top 2 percent of taxpayers. Yet whenever Obama touts his "balanced approach" to the nation's debt problem, this is exactly the plan he describes.

Here's the problem. Over the next decade, the Congressional Budget Office projects that the United States will run deficits of $10 trillion, assuming that Congress continues to make policy decisions as it has historically. But things get scarier in the long term. If the U.S. continues on the same trajectory, by the time a girl born today reaches 30, the nation will run an annual deficit of 20 percent of gross domestic product and accumulate debt of nearly 250 percent of GDP. By comparison, the average deficit between 1972 and 2008 was 2.5 percent of GDP. No nation -- not even Zimbabwe or Greece -- currently has a debt-to-GDP of 250 percent. In reality, bond investors are likely to lose faith in the U.S. and trigger a debt crisis far before the nation reaches that point of indebtedness.

Though these problems -- fueled by an aging population and soaring health care costs -- have been brewing for a long time, Obama has not done anything to make the problem better, despite his repeated promises. When he took office, Obama pledged to cut the deficit in half in his first term. Had he accomplished that, the deficit for the 2012 fiscal year would have been $600 billion -- instead, it was $1.1 trillion.

Throughout his presidency, Obama has talked a big game about getting deficits under control while his actions have just meant more spending. This includes an $833 billion economic stimulus package and $1.7 trillion health care law. After 32 months of rhetoric and finger pointing, in September 2011, Obama finally unveiled a document remotely resembling a deficit proposal. This is the $4 trillion plan that Obama proudly touts on the campaign trail. But let's take a closer look at the math.

On the spending side of the ledger, the law includes $1 trillion in already signed spending cuts from last year's debt ceiling deal and $1.1 trillion in "savings" based on the assumption that the wars in Iraq and Afghanistan would have otherwise been fought in perpetuity. The plan also claims $624 billion in reduced interest payments on servicing the debt. Though the proposal sees $577 billion in cuts to Medicare and other government programs, those are mostly offset by $447 billion in new economic stimulus spending. On the revenue side of the ledger, Obama's plan preserves most of the Bush tax cuts, but projects $1.6 trillion in more revenue from raising the rates on higher incomes and closing various loopholes.

Therefore, on closer inspection, the plan is effectively just a big tax increase -- but not nearly big enough to pay for all the new spending expected over the next decade. More significantly, the plan doesn't do anything to address the nation's real long-term problem, which is the unsustainable growth of entitlements.

Confronted in the spin room by The Washington Examiner following the debate, Obama spokeswoman Jen Psaki struggled to defend Obama's budgetary math. "That adds up to a down payment," Psaki ultimately insisted, when pressed on the details of the plan. She then pivoted to attacking Romney's tax proposal.

Obama wants to be able to claim he's both a strong leader willing to make "tough choices" while also portraying himself as a protector of the nation's generous welfare state. He wants to play the responsible adult by calling for more taxes, while also promising to exempt 98 percent of Americans from tax increases. And his math simply doesn't add up.

Philip Klein (pklein@washingtonexaminer.com) is a senior editorial writer for The Washington Examiner. Follow him on Twitter at @philipaklein.