"The magnitude of the tax cuts that you're talking about, Governor, would end up resulting in severe hardship for people, but more importantly, would not help us grow," Obama said to his Republican rival.
Where does the truth lie in this debate? Is it feasible – and economically helpful – to try to hit Romney's 20 percent target?
To some extent, the answer will be in the eye of the beholders. Voters will render a ballot-box verdict on whose overall vision they find more persuasive, this issue included.
But as US citizens weigh the candidates and their plans, economists and policy analysts offer the following points, which could help clarify the choice:
Romney's "20 percent of GDP" target for federal spending is ambitious. For context, if federal spending were cut by four percentage points of GDP (about $600 billion) immediately, that would represent cutting about $1 for every $6 spent. Romney would want to achieve this goal by the end of a first term.
The leaders of Obama's bipartisan fiscal commission, Erskine Bowles (D) and Alan Simpson (R), came up with a deficit-reduction proposal that aimed to bring spending down to 21 percent of GDP. Obama's budget calls for a spending total of 22.2 percent of GDP in 2017, the fourth fiscal year after the next presidential term begins.
All those targets come in below what the Committee for a Responsible Federal Budget, a nonpartisan group that urges deficit control, calls a "realistic baseline" based on current policies, in which spending would stay above 23 percent of GDP.
Romney's spending plans are short on detail. He has pledged that "by the end of my first term, I will bring federal spending as a share of GDP down from last year’s staggering 24.3 percent to 20 percent or below."