Democratic gubernatorial candidate Timothy M. Kaine is taking his campaign into the heart of Republican strength in Northern Virginia -- the outer suburbs -- with a call for powerful new tools to curb sprawl.

Kaine spent yesterday campaigning with Gov. Mark R. Warner (D) in Prince William and Loudoun counties, two areas Warner lost in 2001. Last year, President Bush trounced Sen. John F. Kerry (D-Mass.) in both areas.

At a breakfast in Leesburg and later in Manassas and Woodbridge, Kaine told audiences that fixing the traffic problems plaguing the region will require local governments to have better control over development.

"You have got to connect your land use decisions with transportation decisions," Kaine said. "There are some who find that that is a huge and controversial concept, the notion that we shouldn't just automatically rezone and develop everything when the transportation infrastructure isn't in place to support it. I think that is such a common-sense value."

Kaine's political strategy is to break the stranglehold Republicans have had on the rapidly growing communities that ring the close-in suburbs. If it works, political observers said, the lieutenant governor could siphon enough support from these traditionally conservative areas to win what polls suggest will be a close election.

With his proposal, Kaine has cast his lot with the region's slow-growth movement and angered developers who provide much of the cash to support campaigns.

"If he cannot appeal to these voters on ideological ground, then he has to reach them on local issues," said Mark J. Rozell, a George Mason University professor who studies Virginia politics. "If he can persuade enough voters to hold down his losses in those areas, that may be enough."

Kaine proposes that local governments get powers over zoning that would allow supervisors and city councils to reject development plans if roads in the area and the region are too congested to support them.

Republican Jerry W. Kilgore opposes such measures, which are often called Adequate Public Facilities ordinances and are common among Maryland counties.

"This is an attempt by a liberal candidate to provide government with the tools to tell people where they can live," Kilgore spokesman Tim Murtaugh said. "The exurbs are important to us. We feel very good about the fact that people who live there will be on our side."

Kaine has been spreading his message about linking development and traffic issues for months. Last week, he proposed bolstering the broad vision.

"I'll give your community more power to stop out-of-control development that increases traffic," Kaine says in a 30-second television ad airing extensively in the outer suburbs.

Kaine's proposal is the ultimate goal for the region's slow-growth activists, who have been contending for years that local governments need more authority to say no to the tracts of townhouses and so-called McMansions that are replacing wooded lots at a brisk pace.

"That's the big ticket. It sounds exactly like what we've been asking for," said former Loudoun supervisor William Bogard, who was swept into office in 1999 on a slow-growth platform.

Bogard and several other slow-growth supervisors were ousted by voters four years later and got a taste of how fickle the constituency is, Bogard said.

But Andrea McGimsey, spokeswoman for the Campaign for Loudoun's Future, a coalition of civic and slow-growth groups, said finding ways to limit growth and relieve congestion is the "number one thing" in Loudoun.

"This is not a trivial issue. It's our everyday reality," McGimsey said. "I think Tim Kaine has keyed into what a huge issue it is in Loudoun."

But those votes could come at a high price. Kaine has accepted almost $2.5 million from the real estate and construction industries, far more than from any other industry. The proposal to clamp down on development took many of them by surprise.

Groups representing Realtors and homebuilders fired off angry e-mails last week to their vast membership rolls. The Virginia Association of Realtors wrote to its 30,000 members that it is "strongly opposed to giving localities such authority. In the end, proposals such as these will only make development less affordable."

The Homebuilders Association of Virginia urged the Kaine campaign to end the ads. The group said Kaine's proposal would "have a devastating impact on the economy of the Commonwealth."

John Foote, a land-use lawyer in Prince William, said the idea is "a death knell for economic development in Northern Virginia" because construction would halt until road capacity is dramatically increased -- a prospect that he said is unlikely anytime soon.

"He believes that will resonate," Foote said of Kaine. "Who among us is not frustrated with traffic?"

Mo Elleithee, Kaine's communications director, said the Democrat hopes to gain ground by addressing that frustration.

"When it comes to runaway development and its impact on their commutes, Tim Kaine has shown that he gets it," Elleithee said.

Rozell said Kaine still has an uphill fight in the outer suburbs. Those areas are among the Republican Party's most reliable. Warner came up short by about 3,500 votes in Loudoun and Prince William in 2001. Kaine, who ran for lieutenant governor that year, also lost both jurisdictions.

"I'd be hugely surprised if after Election Day we saw Tim Kaine doing very well in the exurban communities," Rozell said. "This may be more about holding down his losses in those areas."

Staff researcher Derek Willis and staff writer Timothy Dwyer contributed to this report.

Lt. Gov. Timothy M. Kaine (D), left, and Gov. Mark R. Warner (D) in Manassas.Lt. Gov. Timothy M. Kaine, center, and Gov. Mark R. Warner, left, tour a Virginia Railways Express station in Manassas. Timothy M. Kaine meets with Jane Thompson and Bruce Smith at Dixie Bones restaurant in Woodbridge, an area that Democrats have found hard to crack.