Gov. Mark R. Warner (D) said yesterday that Tuesday's referendum on a Northern Virginia transportation tax remains "a close vote," despite a $2 million fundraising advantage that fellow proponents enjoy over opponents, who have raised or spent about $200,000.

"The opposition has an easier task," Warner said during his monthly Washington area call-in show on WTOP radio. "We're asking people to do something hard -- we're asking them to go out and raise their own taxes.

"The opposition continues to throw up arguments that I don't think carry a lot of water, but they constantly try to plant a seed of doubt," he added.

The Democratic governor said he was "frustrated" by the "sound-bite" politics that he said anti-tax activists and environmentalists are using to stay competitive in the referendum fight, one of the most closely watched races in the Washington region this election season.

Internal polling by a group of transportation tax proponents closely allied with Warner, as well as a recently published survey of voters across Northern Virginia, show Warner's side leading but not by a margin wide enough to ensure victory.

On Tuesday, voters in nine jurisdictions across Northern Virginia will decide whether to raise the sales tax rate from 4.5 percent to 5 percent, which would generate an estimated $5 billion over 20 years for local highway and mass transit programs.

Warner and other proponents said that approving the higher tax is crucial to the region's economic well-being, but the temporary alliance of anti-tax conservatives, slow-growth advocates and environmentalists has raised questions about the need and effectiveness of the tax increase.

Opponents have operated largely on a shoestring budget, according to financial reports both sides have made to the Richmond-based Virginia Public Access Project on money and politics.

Reports filed with VPAP this week showed that two major opposition groups had raised $72,215 over the course of the campaign, and that two other anti-tax groups had raised $38,502.

Two other transportation tax opponents, the Piedmont Environmental Council and the Virginia League of Conservation Voters, reported spending $58,399 and $25,263 respectively, VPAP said.

All told, opponent groups reported raising or spending $194,000, or less than a tenth of the $2.1 million raised by the Citizens for Better Transportation, the umbrella group of proponents backed by Warner. As it has throughout the campaign, CBT reported receiving several developer contributions in the $25,000 to $50,000 range during October.

Both sides have been saving sizable chunks of their resources for last-minute ad blitzes on radio and TV while concentrating on identifying their respective voters through telephone banks.

Proponents have about $500,000 left, putting them in a better position financially to mount a TV and radio campaign; opponents said they will have about $50,000 heading into the final days.

State Sen. Ken Cuccinelli (R-Fairfax), a leader of the opponents, said the pro-tax side's advantage in media money at the end of the race was daunting but may be too late to make a substantial difference.

"Apparently, it takes more than $2 million to overcome the facts," Cuccinelli said, referring to a recent survey by Mason-Dixon Polling & Research Inc. that showed proponents leading, 49 percent to 43 percent, with 8 percent undecided. The survey of 400 self-described likely voters had a margin of error of plus or minus 5 percentage points.

"The more people know about the referendum, the less they like it," Cuccinelli said. "The other side needs to be close to 60 percent to win. Their people are not as intense as ours."

Mary A. "Mame" Reiley, chief strategist for the proponents, said her side was not taking any polling lead for granted.

"We are solidly ahead, but we are approaching it like the fight of our lives," Reiley said. "We have organizational superiority, but we're giving this everything we've got."

Gov. Mark R. Warner (D), right, joins Sen. John W. Warner (R) and Rep. Thomas M. Davis III (R) to discuss the transportation referendum in Springfield.