Virginia's Democratic governor and senior Republican senator teamed up on a political ad yesterday, standing before a camera crew at a Metro station in Northern Virginia to urge approval of a sales tax increase that would finance transportation projects.

Sen. John W. Warner then joined Gov. Mark R. Warner, the Democrat who tried to unseat him in 1996, in a daylong barnstorming tour of the state's urban and suburban corridors, exhorting voters -- from Tysons Corner tech workers to Newport News shipbuilders -- to approve the tax. Hampton Roads, like Northern Virginia, votes Tuesday on a transportation tax proposal.

With less than a week to go, the two sides in the Northern Virginia tax debate are reaching out to voters with direct mail, phone banks, get-out-the-vote rallies and, for the governor, multiple swings through the suburbs. He plans to return to Arlington tomorrow for a rally with groups that have endorsed the tax.

Anti-tax activists said they are working hard at the grass-roots level to get out their vote, lining up supporters through local Republican committees that oppose a tax increase.

"We don't have all the money they're using to impose this tax, but what we have quite simply are the people," said James T. Parmelee, a leader of the coalition fighting the proposed tax increase.

The anti-tax campaign put up signs in Baileys Crossroads last night. On Monday, the activists held a rally with Jack Kemp, the former presidential candidate and Housing and Urban Development secretary. On Saturday, they plan a get-out-the-vote rally in Burke.

"Their message is not selling," Parmelee said of the tax's supporters. "The question is, is there enough time left and who's motivated to come out to vote?"

Both sides say the contest is close. Proponents, including many local governments as well as business and civic leaders, say the increase in the sales tax of a half-cent per dollar would help Northern Virginia solve its own transportation problems.

Opponents, including environmentalists, slow growth advocates and anti-tax conservatives, say the higher tax would benefit only real estate developers who want more roads sprawling across the suburbs.

The Warners' partnership began at rush hour yesterday morning at the Dunn Loring-Merrifield Metro station along Interstate 66, where the campaign for the tax was launched last summer.

"The governor and I are working as a team to improve transportation in Northern Virginia," Sen. Warner said, as the camera rolled just after 8 a.m. The view took in four lanes of cars and trucks at a standstill on the highway below. "But we need your support on the referendum."

"Together we can improve our congested roads, expand Metro and [Virginia Railway Express] and finally bring rail to Dulles," Gov. Warner continued, standing shoulder-to-shoulder with the senator.

Tax proponents plan to air the ad on Washington-area television stations in the next five days, part of a $350,000 effort that began late last week.

Voters in nine counties and cities in Northern Virginia will decide whether the sales tax rate rises to 5 cents per dollar, generating an estimated $5 billion over 20 years for road and mass transit improvements.

Sen. Warner has stood with the governor at several pro-tax events, a show of bipartisan support that advocates count on to bring out the vote in a year when Virginia has few contested elections.

"We just put politics aside and get on with it," said the senator, who is seeking a fifth term Tuesday. "Getting this passed is our joint responsibility."

While the senator is one of Virginia's most popular political figures, the value of his endorsement remains unclear. The governor put a premium on the Republican's support, courting him throughout the summer, but many conservative GOP voters have been uncomfortable with the senator's stand.

After filming the ad, the Warners, who are not related, headed to Tysons Corner. The region's symbolic Main Street and biggest shopping center, Tysons Corner Center, was just stirring to life, as janitors swept floors and stores prepared for the day.

The two promoted the tax to salespeople and other workers, then did the same to about 200 employees gathered at the Northern Virginia officers of Capital One, a financial services firm. Business leaders have been the largest financial backers of the pro-tax campaign, viewing traffic congestion as a potential threat to commerce.

Rodney Gray, a contractor at Capital One, said he drives 25 miles from his Leesburg home to the office every day, a 90-minute trip that grew longer with yesterday's rain.

"I'm on the edge of my seat waiting for a rail line to Dulles," he said, referring to one of the projects that would receive partial funding from the proceeds of a tax increase. "But I'm still torn on the referendum, since it's a tax increase."

The governor and senator also made a pitch for two statewide bonds on the ballot that would raise millions of dollars to acquire parkland and build new research labs and classrooms at Virginia colleges and universities. Later, they campaigned in Newport News, where a one-cent sales tax increase is on the ballot next week.