Every October the mood turns sour in Prince William County as thousands of residents, many of them muttering and grumbling, rush to meet the deadline for payment of the personal property tax.

This year, the annual chorus of discontent has risen in volume and irritability, with several candidates in the Nov. 3 general election joining in to denounce and vow to eliminate the highly unpopular tax, paid primarily on motor vehicles and boats.

As the tax has become an issue in many races for the Prince William Board of County Supervisors and the Virginia General Assembly, the disdain many residents feel toward the annual levy is clear. Less obvious, according to critics, is what alternatives exist to replace the nearly $21 million the tax is expected to raise this year for the county, and whether promises by some candidates to do away with it have any credibility.

"I feel the tax is highly discriminatory," said Gregory L. Cebula, a Republican candidate in Prince William's Occoquan District, who has made elimination of the personal property tax a centerpiece of his campaign. "A car is not a luxury; it's a necessity."

"It's an onerous tax -- we all hate it," agreed Supervisor Kathleen K. Seefeldt, Cebula's Democratic opponent. But she quickly added, "You can't eliminate it -- to talk otherwise is magic-carpet time."

Others disagree, and not just in Prince William. In a debate yesterday before the Fairfax County Chamber of Commerce, a proposal to eliminate the tax by James S. Morris Jr., an independent waging a long-shot candidacy for the chairmanship of the Fairfax County Board of Supervisors, drew a burst of spontaneous applause.

At $3.75 per $100 of assessed value, Prince William's personal property tax is lower than those of most other Northern Virginia localities -- Fairfax County, for example, charges $4.57 per $100 of assessed value -- and over the years, the tax has been an election-year issue in several races.

Last year the tax accounted for 11 percent of Prince William's county-raised revenue, the bulk of which comes from its real estate tax of $1.30 per $100 of assessed value.

Nonetheless, in recent years the unpopularity of the personal property tax has risen, according to county politicians. Unlike the real estate tax, which is usually paid monthly with the mortgage, the personal property levy is due annually in a lump and seems to catch many residents by surprise. The pinch is especially hard on lower-income families or fixed-income retirees, critics contend.

Of course, the tax hits people differently: The owner of a $500 jalopy pays $18.75 at tax time; the person who cruises in a $40,000 Mercedes-Benz, by contrast, owes $1,500.

Seefeldt and other defenders of the personal property tax said candidates who propose to scrap the levy carry the burden of explaining precisely how they would cut county spending or otherwise make up for the lost revenue.

Increasing the real estate tax, one way to make up the revenue, would require raising that rate about 31 cents, to $1.61 per $100. Not surprisingly, no candidate has pitched this political stink bomb.

Most of the candidates who propose eliminating the personal property tax claim that the revenue could be recouped through a vague combination of increased governmental efficiency and other revenue sources.

"I am sure there is a lot of waste in our budget," said Cebula. "I have-n't thought out the solution at this time."

Nonetheless, Cebula has been more precise than have most other critics of the personal property tax. In last spring's county budget process, he advocated several specific spending cuts, and a real estate tax rate higher than what the supervisors eventually approved, to eliminate the personal property tax.

By contrast, Hilda Barg, a Democratic candidate for supervisor in Prince William's Woodbridge District, said "there are many ways" to replace the personal property tax, including an increase in the sales tax and the imposition of "impact fees" on developers.

However, both these measures would require action from the Virginia General Assembly, which state political observers consider a virtual impossibility.

"I'd like to think that we can eliminate tax without adding tax" or imposing harsh cuts on county programs, said Barg.

Her opponents in the Nov. 3 election, Republican Ella Shannon and independent Edward Rodriguez, have called this thinking unrealistic.

Democratic state Sen. Charles J. Colgan, one of Prince William County's fiercest opponents of the personal property tax, said he recognizes the political limitations on scrapping a large funding source in a single fell swoop. However, the tax could be made less burdensome by allowing staggered payments and exempting needy individuals, he said.

Colgan also criticized recent legislation, sponsored by Rep. John A. (Jack) Rollison III (R-Prince William), that allows the county to prorate its property tax on vehicles from the date of purchase. Before, residents paid tax only on vehicles they owned as of Jan. 1 in a given year.

Rollison's Democratic opponent, George N. Dowd, also has criticized Rollison for pushing the measure through the General Assembly.

Despite the election-year rhetoric, an increase in Prince William's real estate or personal property tax rate -- or perhaps both -- seems certain next year, many county officials concede privately.

Earlier this year the supervisors, a majority of them heading into reelection battles, slashed both tax rates, saying the county had successfully broadened its tax base by attracting new businesses.

At the same time, however, the supervisors decided not to fund proposed improvements to the county's badly strained public facilities, and spent a large portion of a "contingency" fund. If these items are restored in next year's postelection budget, significant tax increases will be required, county officials said.