Del. Walter E. Fauntroy (D-D.C.) was the first of this year's mayoral contenders to suggest putting the bite on Maryland and Virginia residents by imposing a tax on commuters' incomes.

Election season is the time when talk of a commuter tax traditionally flourishes. And as the District prepares to elect a new mayor, a new D.C. Council and a new delegate to Congress, candidates are looking for ways to finance the government without raising taxes for city voters.

Now the city's Commission on Budget and Financial Priorities, which has been looking for ways to solve the city's financial crisis, also is exploring the commuter tax as a way of raising additional money for the District.

"It's just not fair that commuters who hold half of the city's jobs expect those who live here to pay for 100 percent of the cost or repairing the roads and bridges they use to get here and the police and other services we provide them," Fauntroy said.

In many other metropolitan areas -- Philadelphia and New York, for example -- commuter taxes have long been a part of life.

But the District is legally barred from taxing commuters; members of Congress from Maryland and Virginia inserted a clause banning such a tax in the charter that granted self-government powers to the District in 1973.

Only an act of Congress could allow such a tax, and a close look at the impact shows that lawmakers from Maryland and Virginia would have little incentive to back such a measure.

Fauntroy has said he plans to lobby Congress to amend the charter to allow the tax. But D.C. Council Chairman David A. Clarke, a Democrat also running for mayor, says Fauntroy as mayor would have no chance of convincing Congress.

"For 19 years Walter Fauntroy hasn't been able to do it," said Kerry Pearson, Clarke's campaign manager. "What makes him think that after he leaves Congress that he will be able to do it?"

If commuters' incomes were taxed at the same rate as D.C. residents, the effect would be a financial windfall of more than $1 billion for the District, officials said.

The effect on the suburbs is more surprising: Commuters who pay the tax might feel only a limited financial pinch, while the impact on state governments in Virginia and Maryland could be significant.

Because the tax rate in the District is higher, the tax bills of Maryland and Virginia commuters would increase somewhat. But officials in both states say commuters would be allowed to deduct any tax they pay to the District from what they pay to their home state.

They also say that would wipe out all the income tax revenue both states collect in the Washington suburbs and wreak havoc on budget-makers in Annapolis and Richmond.

Even if the District taxed commuters at a lower rate than residents, a standard that is common in other areas, the loss of revenue could create major money trouble for the states. Virginia and Maryland would be forced to look for new revenue sources or a change in tax laws to shift the commuter tax burden directly onto those who pay it.

"There would be a direct, dollar-for-dollar reduction in revenue to the state of Maryland," said Ken Mannella, a tax specialist in the state of Maryland's Washington office.

Virginia Tax Commissioner William Forst said that more than a third of his state's income tax collections come from Northern Virginia. A commuter tax would mean that "every resident of Virginia who works in the District wouldn't pay Virginia income tax any more," he said.

Yet in many parts of the country, commuter taxes have been a fact of life for decades. And most are income taxes applied to the paychecks of people who work in a city but live in the suburbs.

A recent study by the Advisory Commission on Intergovernmental Relations showed that most cities levy a flat-rate tax somewhat lower than the tax charged to city residents.

New York City, for example, levies a tax of 0.25 percent on commuter incomes; residents pay income tax at rates ranging from 1.5 percent to 3.5 percent. In Philadelphia, commuters pay 4.315 percent and residents pay 4.96 percent.

Virginia and Maryland lawmakers who oppose a commuter tax argue that it is inherently unfair because it forces nonresidents to support a government whose leaders they have no part in electing.

They also argue that commuters contribute significantly to the District through taxes on restaurant meals and retail purchases made in the city.

Proponents say nonresident taxes help pay for essential city services that commuters use, such as streets and utilities. And in parts of the country where Congress has not specifically outlawed commuter taxes, courts have agreed. Since the early 1960s, major court decisions have upheld the legality of many commuter taxes.

As part of the 1991 budget, District officials projected what would happen if Virginia and Maryland commuters were taxed at the same 9.5 percent rate on incomes over $20,000 as D.C. residents.

The District, the study showed, would gain almost $1.2 billion in revenue, while Virginia would lose more than $593 million and Maryland would lose more than $650 million.

Rep. Stan Parris (R-Va.) said such revenue losses "would be disastrous." Parris calls a commuter tax "faulty public policy and an irresponsible evasion of the {District's} obligation to get its fiscal house in order."

Robert Pohlman, the District's deputy mayor for finance, said all 50 states have the authority to levy commuter taxes, and the District is the only jurisdiction that can't.

"The District is in a double bind" because commuters cannot be taxed and because the federal government has not increased its payment to the District for several years, Pohlman said. "Equity would call for a solution involving one or both of these areas."