Transportation tax proponents in Northern Virginia are starting to broadcast their advocacy message on expensive Washington television as the two sides of the sales tax referendum campaign begin their final push to the Nov. 5 election.

"It is get-out-the-vote TV," said Mary A. "Mame" Reiley, chief strategist for the pro-tax group that will spend at least $350,000 on broadcast and cable television ads between now and election day.

Two TV ads sponsored by Citizens for Better Transportation will air at a critical juncture in the campaign, as voters across the suburban region begin to focus on the tax debate following the arrest early yesterday of two suspects in the Washington area sniper investigation.

The ads coincide with the group's $50,000 program of radio ads during morning and evening rush hours, as well as a direct-mail push by opponents of the transportation tax, including an environmental coalition and anti-tax conservatives.

Voters in nine Northern Virginia jurisdictions go to the polls in 11 days to decide whether to raise the sales tax rate from 4.5 percent to 5 percent on most goods, generating an estimated $5 billion over 20 years for local highway improvements and mass transit projects.

The debate on the ballot question, like most other politicking in the Washington area, has been muffled for three weeks by the sniper killings.

State Sen. Ken Cuccinelli (R-Fairfax), a leading opponent of the tax, agreed with Reiley that the arrests will free pent-up organizing energy. "We're going to be able to turn our people loose," Cuccinelli said. "We had people just waiting to go door-knocking -- who wouldn't until now."

Cuccinelli said the Citizens for Better Transportation's television ad effort was "daunting" but could be offset by an energetic grass-roots network of opponents.

"I'm worried about their massive dollar amounts, but I don't know how decisive it will be," Cuccinelli said. "In other referendums at this late stage, undecideds tend to break against a tax increase."

The ads show harried drivers -- one man climbing into his car in the pre-dawn darkness and a soccer mom who complains that "traffic was so bad, we missed half her game." Both ads try to reassure voters that money raised in Northern Virginia will stay in the region, a key point of contention in the referendum debate.

"What we're trying to make sure is that people realize this is our chance," said media consultant Joe Trippi, who designed the TV ads. "The ads say: Everyone knows traffic's a big problem, and we can do something about it."

But Cuccinelli countered that voters remain distrustful of the General Assembly's intentions for any new sales tax revenue generated by the Washington suburbs.

He issued a statement yesterday on the Web site of the Coalition Against the Tax Referendum that "condemned" Gov. Mark R. Warner's creation of an audit committee to ensure that Northern Virginia sales tax revenue stays in the region. Warner (D) is a leading champion of the sales tax increase.

"Our analysis indicates that is is clearly contrary to the law of Virginia," said Cuccinelli, a patent lawyer. "This is another desperate attempt by the governor to try and trick the voters into thinking that these funds cannot be diverted -- history proves otherwise."

Ellen Qualls, Warner's press secretary, said that Warner had clear authority to create audit committees by executive order, adding that the code section cited by Cuccinelli applied only to minor advisory commissions and gubernatorial study groups.

"This is just another red herring" by opponents of the transportation tax, Qualls said.

Reiley acknowledged that some voters are still skeptical that the sales tax revenue will benefit only Northern Virginia, which is why both ads say the money will be used exclusively for local projects.

"One hundred percent of the money raised here, stays here," Reiley said. "That point needs to be driven home."

Supporters of a sales tax increase that will generate funds for road improvements and mass transit are launching ads aimed at commuters.