How is it that Romney, Santorum, and Gingrich would end up increasing the federal debt? It’s pretty simple, really: They would cut taxes, but wouldn’t cut spending to match. Santorum’s policies would reduce spending by a little more than $2 trillion, but would cut taxes by $6 trillion. Gingrich would cut slightly more in spending—about $2.7 trillion—but would cut taxes by $7 trillion and actually add $1.6 trillion in spending to overhaul Social Security, among other policy changes. Romney’s vague plans score better, but wouldn’t reduce the debt, and would probably push it slightly higher than it otherwise would have been. Ron Paul, on the other hand, would cut taxes, but he’d cut spending even more. His tax cuts would reduce the tax burden by $5.2 trillion; meanwhile, he would reduce spending by $7.2 trillion.
Derek Thompson puts the candidates tax plans in context:
These plans don't accidentally raise the deficit. They just don't care about the deficit. Deficit reduction isn't hard to do, arithmetically. You raise taxes over time. You control discretionary spending. You clear the way for health care cost innovation while introducing policies that will limit health care in the future. It's not rocket science, it's math. The hard stuff is getting Congress to agree to your math. But how is that supposed to happen if pols refuse to do even the basic addition and subtraction when it's just them and a blank sheet of paper?