For Republican James S. Gilmore III, his campaign to be Virginia's next governor may well rest on this: how angry he can make Northern Virginians during the next few days.

With hundreds of thousands of people in Washington's voter-rich Virginia suburbs writing checks this week to pay the state's property tax on their cars and trucks, Gilmore has launched the most aggressive ad blitz of his campaign, aimed at stirring voters' hatred of the unpopular levy and promoting his plan to virtually eliminate it.

The $1 million-plus effort promotes the centerpiece of the Republican's campaign and is built around the Monday due date for the tax in jurisdictions across affluent Northern Virginia.

Gilmore believes his anti-tax message will resonate in Northern Virginia because local rates for the tax are among the highest in the state, and residents there typically drive more expensive cars than Virginians elsewhere.

It's also an area with a fourth of the state's 3 million voters, and the home turf of Gilmore's Democratic opponent, Lt. Gov. Donald S. Beyer Jr., of Alexandria.

In recent days, the state's Republican Party has buried 200,000 Northern Virginia households with the latest in a series of mail ads trumpeting Gilmore's pledge to phase out the tax on the first $20,000 of value of cars and trucks over five years. On television, Gilmore, a former state attorney general from suburban Richmond, has put up 10- and 30-second ads nagging suburbanites: "Paid your car tax yet? Jim Gilmore says, Enough's enough.' "

It's a taunt that Republicans hope will help them build an anti-tax bandwagon that will break open a tight race and carry Gilmore through the Nov. 4 election.

"Even after you pay it, you're still going to be mad for four weeks because your cash flow is messed up," said Gilmore media consultant Dick Leggitt.

Rarely, if ever, has a Virginia governor's race been influenced so much by a quirk of the tax calendar, analysts say. Since Gilmore unveiled his plan last spring, and Beyer answered in July with his own tax-credit plan based on what residents pay on the vehicle tax, no issue has dominated the governor's race like the $1.2-billion-a-year personal property levy.

The issue is particularly potent this fall in Northern Virginia, where jurisdictions collect the tax every October. Many jurisdictions elsewhere do so in the spring.

Although Beyer's plan is more generous in tax relief than Gilmore's in its early years, he has not made it the focus of his campaign ads, which in recent days have pushed not just the Democrats' tax plan but his education and environmental stands. Gilmore, meanwhile, is saturating Washington's airwaves with his tax-cut plan.

The drive to slash the car tax, which began last winter as a legislative proposal from a Prince William County Democrat, could reshape the state's traditional political landscape.

Gilmore's proposal is winning him support in high-tax areas of Northern Virginia, cutting into Beyer's support base. Beyer, meanwhile, has shown surprising strength in more conservative, rural areas downstate, where tax rates are lower and the Democrat's proposals to improve schools seem to be playing well.

A Washington Post voter survey two weeks ago showed Beyer with only a slight lead over Gilmore in Northern Virginia, 45 to 43 percent.

"I think the momentum may be better than that," Gilmore boasted this week. "We think the people of Northern Virginia are rallying very much to my plan to abolish the tax on cars and trucks."

Beyer, who owns two import car dealerships, has attacked Gilmore this week as anti-education and anti-environment, and soon will focus on the Republican's antiabortion views.

The Democrat played down the Northern Virginia poll numbers, noting the race is deadlocked statewide, and said the race will "bust wide open" when many voters learn of Gilmore's past stands against abortion after the first trimester even in cases of rape or incest, his support for using public funds to give parents vouchers to send their children to private schools, and the true cost of Gilmore's tax-cut proposal, which some estimates place at $3 billion.

"I keep reading these stories that this race is only about the personal property tax," Beyer said. "Nothing could be further from the truth.

"This race is about who's got the bolder vision for education. The other guy's {tax-cut} plan costs $3 billion over five years; my plan costs $1 billion. That $2 billion is the difference in what we're going to invest in our children and grandchildren."

Although 60 percent to 80 percent of voters have told statewide pollsters they don't like the vehicle tax, many can't distinguish between Gilmore's pledge to gradually wipe out 90 percent of the tax, and Beyer's plan to give an immediate tax credit worth up to $250 a year for lower- and middle-income voters.

Voters also seem torn between the emotional appeal of a pocketbook break and what their heads say is important. Although they hunger for the tax cut, voters by 2 to 1 say education spending is needed more urgently.

"Part of me says they might have to raise the income tax or sales tax or some other tax to cover" a tax cut, said Robert F. Fertig, a 38-year-old AT&T engineer from Sterling Park in Loudoun County. "But I'm all in favor of getting rid of that car tax. That's a pain."

Fertig owes $700 in taxes on his 1995 Ford 150 pickup truck and a 1989 Taurus, and calculates that under Gilmore's plan, he'd eventually be "scot-free."

As the campaigns push voters to make up their minds, the battlefield of the moment is on Washington's doorstep, several analysts said.

Yesterday, hundreds of taxpayers milled around Fairfax County's government center to pay their tax bills, where the Gilmore campaign had plastered red, white and blue "No Car Tax" posters everywhere in sight.

And outside a Wal-Mart on Route 1, enterprising Republicans even nailed the slogan to wooden Fairfax County signs reminding residents that the tax is due. Staff writers Mike Allen and Eric Lipton contributed to this report. CAPTION: James S. Gilmore III (R) has launched an aggressive ad blitz. ec