Aredrawn Virginia Senate district straddling Fairfax and Prince William counties is the battleground in a short but lively race between a school activist from Franconia and a longtime state delegate from Clifton.

Democrat Rosemary M. Lynch and Republican J.K. O'Brien Jr. are facing off for the open seat, the only General Assembly race in Northern Virginia on Tuesday's ballot. O'Brien, a six-term legislator, is stressing what he calls his "conservative Republican" credentials, while Lynch is calling herself a more moderate candidate who will fight to increase funding for public schools.

Both candidates, knocking on doors and shaking hands at grocery stores in a compressed special election campaign, also are hoping to stir support from voters who have been more focused on the recent sniper shootings and the sales tax referendum than on their Senate race. O'Brien opposes the proposed half-cent tax increase for transportation improvements that is on the ballot, whereas Lynch supports it.

When voter Pam York shook Lynch's hand recently as she campaigned at a Giant supermarket in Springfield, she asked the candidate exactly what the sales tax money would be used for.

"It's for roads and mass transit improvements in Northern Virginia, and the money stays here" rather than going to the state treasury in Richmond, Lynch explained. "I'm there for that," said York, a U.S. Postal Service executive who votes Democratic.

O'Brien, meanwhile, tells voters he believes that having the region tax itself to pay for solutions to its traffic problems is the wrong way to uncork Northern Virginia's gridlock. State government cannot be left off the hook, he said; it would set precedent that the region does not need as much help from Richmond.

"My view is, if we are important to Virginia, then when we're in our hour of need, we should get funding for roads," O'Brien said.

The candidates also want to make sure voters know their differences on other issues.

O'Brien, who with his wife, Sevea Grace Staves, runs a business selling office products to retail dealers, is highlighting his legislative record in the Virginia House of Delegates. In the past two years, he co-sponsored laws restricting teenage drivers and toughening penalties for aggressive driving. Several years ago he championed a law raising education standards for substitute teachers. He said he is also proud of authoring the state law allowing organ donors to indicate their preference on their driver's licenses.

"I bring a lot to this race as a credible officeholder," O'Brien said.

Lynch, a former chairman of the Fairfax County Council of Parent-Teacher Associations and director of a trade association, calls education her "biggest issue." She cites her 30 years as a school activist as her best credential for getting more state funding to build new schools and support the day-to-day operations of existing ones.

She accused O'Brien, who supports school vouchers, of neglecting the public school system.

"He has not been a champion for education," Lynch said. "That's why I felt it was time for me to step up" and run for office. Lynch's three children attended Fairfax public schools.

O'Brien, whose five children attend parochial schools, bridled at the suggestion that he does not support spending for public schools. He said he did not support a bill when the legislature was in session last winter that would have set aside a half-cent sales tax increase for school construction, because some of the money would have gone outside Northern Virginia.

O'Brien also cited a bill he sponsored expanding retirees' ability to take courses free at Virginia's public universities.

Lynch, a breast cancer survivor, said she would fight to lengthen hospital stays for cancer patients and increase prescription drug benefits for the elderly.

The 39th District was created last year as part of the General Assembly's efforts to redraw districts to reflect the 2000 Census. The district of 100,000 people stretches from Franconia west to Clifton in Fairfax County and runs south into Prince William, including Lake Ridge and the Occoquan watershed. Eight of the district's 37 precincts are in Prince William.

O'Brien and Lynch announced in August that they would run, after the unexpected retirement of a Roanoke senator whose district was moved north to accommodate population growth in Northern Virginia.

Fairfax Democrats are fighting to keep the 39th seat after their defeat in August in another special Senate election in the neighboring 37th District in southwestern Fairfax, won by Republican Ken Cuccinelli of Centreville.

The Lynch-O'Brien matchup also is being closely watched by state party leaders. Republicans hold a relatively narrow 22-18 edge in the state Senate.