House Democratic leaders want to tax the wealthy to pay for health care reform while others want to tax them to pay for the war in Afghanistan.

But the proposed tax surge simply reflects the bind Washington is in: The federal government has excluded so many from the tax rolls -- one third of American tax filers now pay no income taxes -- that it gets increasingly hard to raise revenue.

"That's more than 46 million tax filers have zero income tax liability at the end of the day" because of tax credits, Scott Hodge, president of the Tax Foundation, told Fox News.

Another 15 million people earn so little that they don't even file income tax returns, though all wage earners pay a flat payroll tax to fund Social Security and Medicare.

One reason the high number of Americans paying no federal income tax is that tax credits have proliferated. A family with four children that makes $35,000 to $40,000 a year, for instance, can pay no income tax.

And even those who owe no tax still can get some credits, providing them a check from Uncle Sam.

"The people who don't pay taxes have less of a stake in what government does with the money that's collected by the Treasury," financial columnist Jim Glassman told Fox News. "It's very hard to enact at this point sensible tax policy because so many people aren't paying taxes."

"We've inoculated these people from the cost of government," Hodge said. "They no longer have a skin in the game. And so they'll endlessly demand government benefits because they're not sharing in any of the cost?

That also leads to another problem. The president and others say they only want to tax the rich, those making more than $250,000. But they may have to raise taxes sharply to cover all the things Congress and the president want to do.

"There is just not enough money up there," Robertson Williams, a senior fellow at the Urban Institute, told Fox News. "We can't tax only the rich the way President Obama proposed."

In fact, the Tax Foundation looked to see what it would take to balance the budget over the next 10 years taxing only the wealthy.

"You need to increase their tax rates by about 30 percentage points," Williams said. "We're talking about marginal tax rates in the 60 to 70 percent range."

Rates that high haven't been seen since the 1960s. There was a much narrower gap back then between the rich and poor in America, but some argue that returning tax rates to those levels now would reduce business investment, hurt the economy and reduce jobs.

Jim Angle currently serves as chief national correspondent for Fox News Channel (FNC). He joined FNC in 1996 as a senior White House correspondent.