To see where the presidential candidates stand on taxing the rich, just look at how they'd tax themselves. Under his own proposal, Mitt Romney would pay half what he would under President Barack Obama's tax plan. For a man of Romney's means, that could save almost $5 million a year.

For Obama, not so loaded as Romney but still well-off, losing re-election could provide a tax windfall. He'd save as much as $90,000 a year if Romney's plan were enacted rather than his own tax-the-rich vision.

Two nonprofit research groups, the liberal-leaning Citizens for Tax Justice and conservative-leaning Tax Foundation, did the calculations, based on the most recent completed tax returns released by the candidates. Compared with what they owed in April, both men would be dinged in 2013 under Obama's proposal, along with other wealthy taxpayers. They could expect savings under Romney, depending on which tax breaks the former Massachusetts governor decides to oppose.

Whether they go up or down, the candidates' personal tax bills won't make a dent in the nation's trillion-dollar annual deficits, of course. But they illustrate a sticking point in the struggle to fix the nation's finances: Just how much should affluent Americans pony up?

Democrats generally say the rich aren't paying their fair share; most Republicans argue that raising taxes on the wealthy would slow investment that creates jobs. The dispute makes it tougher to tackle urgent budget issues, such as whether to extend the Bush-era tax cuts again before they expire Jan 1.

Support for continuing the tax cuts for the middle class is wide, but a fight is under way over what to do about the wealthy.

"There's quite a difference at higher incomes between the Obama and Romney plans," said Gil Charney, principal tax researcher for the Tax Institute at H&R Block. "Obama is looking at the rich - millionaires and billionaires - as a source of additional revenue to the government, where Romney is looking at them as a potential spark for economic growth."

Obama's plan would hit couples making more than $250,000 per year from several directions, raising their tax rate, dunning them more for investment income, and limiting their tax deductions. People like Romney with earnings from private equity management would lose a big tax break. And Obama would establish a rule, named after billionaire Warren Buffett, to ensure that households taking in more than $1 million a year pay at least 30 percent in taxes.

Obama's health care law, already in place, also raises Medicare taxes on the wealthy, especially big investors, starting in 2013. That could cost Romney more than $800,000.

None of this would come close to balancing the budget, but it could add billions of dollars per year to help reduce the deficit.

Romney wants to lower current tax rates for everyone by 20 percent. This benefits the wealthy most: Dropping the highest bracket from 35 percent to 28 percent, for example, yields a much bigger savings for those at the top than lowering the 15 percent bracket to 12 percent brings for taxpayers in that group.

Romney also would eliminate the much-despised alternative minimum tax, which hits the rich and some middle-class taxpayers, too. He wants to repeal Obama's health care law and its taxes. Romney would pair his tax cuts with huge spending reductions eventually reaching $500 billion per year.

To help offset the government's losses from lower rates, Romney says he would end some tax breaks. But he hasn't said which ones, so it's impossible to calculate the effect.

At the extreme, if Romney persuaded Congress to eliminate all itemized deductions - hard to imagine politically - that could add another $1.3 million to what he owes under his own plan, according to Tax Foundation analyst Nick Kasprak.

Under that scenario, Romney's bill would still be $3.5 million less than under Obama's plan.

Kasprak expressed skepticism that Romney would target enough tax breaks to offset the tax cuts he proposes.

"You'd have to get rid of the vast majority of deductions and credits in the tax code to make it work, including some sacred cows like the mortgage interest deduction, child tax credit, etcetera," Kasprak said.

Spokeswoman Andrea Saul said Romney envisions changes to create a "fairer and simpler tax system," but did not give details.

Here's how the plans the two candidates have described so far would play out in 2013. The numbers are from calculations by Citizens for Tax Justice, corroborated by the Tax Foundation (although it would use slightly lower figures for Obama that exclude employer-paid Social Security and Medicare payroll taxes):

ROMNEY

Assuming inflation-adjusted earnings of $23 million, he'd pay an effective rate of 34 percent under the Obama plan. That drops to 13 percent under Romney's own tax proposal - even lower than the 15 percent he estimated for 2011, which irritated critics who felt a multi-millionaire investor should shoulder a higher rate than middle-class working families.

The difference between the two candidates' plans: paying the taxman $7.8 million vs. $3 million.

OBAMA

Like others who are taxed at earned income instead of investment rates, Obama's bill wouldn't swing as dramatically under the differing plans. He reported paying an effective tax rate of almost 21 percent on about $790,000 in income in 2011. Under his own plan, that would climb to 28 percent. Under Romney's plan, it drops to 18 percent.

The difference: $248,000 vs. $158,000.

The figures were based on Obama's 2011 tax return and Romney's 2010 return. Romney has filed for an extension and released only preliminary 2011 numbers.

Bob McIntyre, director of Citizens for Tax Justice, said Romney's savings for the wealthy come at the expense of everyone else.

"If we have more tax cuts for the rich, or even keep the ones we have now, then somebody's got to pay for it," McIntyre said, either in higher taxes or by losing government services.

At the Tax Foundation, Kasprak called Romney's plan a step in the right direction because it would lower tax rates overall and thin the tangle of deductions and credits. He called Obama's proposal "complex and arbitrary."

Odds of either candidate getting his full plan through Congress after the Nov. 6 election are slim. Efforts to reform the tax code have been mired in partisan bickering for years. But pressure is building to do something.

"Just because Romney wins or Obama wins doesn't mean that what they're proposing becomes law," said Charney of H&R Block. "What may be more likely is bits and pieces happening."