By most measures, Northern Virginia is the colossus of the commonwealth, supplying about a third of the state's voters, the engine of its economic growth, the center of its wealth. Lop it off at the Rappahannock River and the State of Northern Virginia would be the richest in the union.

Politicians and demographers looking for clues about how to deliver the area in next month's statewide elections see it as a region with an emerging common identity. But they also see it as a collection of sometimes conflicting territories: the republics of Arlington and Alexandria, the commonwealths of Loudoun and Prince William, the giant United Neighborhoods of Fairfax.

Those differences will be as important to the candidates as the similarities.

Like most everything in Northern Virginia, the political demarcation is paved with asphalt. Interstate 95 is Democratic blue. Interstate 66 is Republican red. And the Capital Beltway is the great divide: Democrats live inside, close to bus routes and Metro stops, and Republicans pack the HOV lanes to get to and from their single-family homes beyond.

"To the rest of the state, Northern Virginia is a single-cell amoeba," said Del. Brian J. Moran (D-Alexandria). "Those of us in Northern Virginia see its individual parts. It's far more diverse than the rest of the commonwealth thinks of us."

Its impact on the Nov. 8 election is indisputable. "It's incredibly important to us in the campaign," said Democratic gubernatorial candidate Timothy M. Kaine, the state's lieutenant governor. "We view it as absolutely critical that we do well." His opponent, former attorney general Jerry W. Kilgore, a Republican, has more staff in Northern Virginia than anywhere outside the campaign's Richmond headquarters.

But their messages and methods of reaching the region's voters illustrate the area's differences.

"There's no silver bullet to getting a Northern Virginia vote. They've proven to be so diverse and independent," said Jim Dornan, a GOP consultant who was chief of staff to then-Lt. Gov. John H. Hager. "You've got to walk through a lot of land mines. The key is going to be to get your base [of supporters] to come out in full force rather than to appeal to everybody on every issue."

In the outer suburbs, where Republicans dominate legislative and local offices and President Bush won a majority of votes last year, a recent Washington Post telephone poll showed transportation tied with schools as the most important issue, and Kilgore has made road-building the centerpiece of his television appeal. In campaign literature, he says he is "committed" to widening I-66 inside the Beltway, a popular position in the exurbs but anathema to heavily Democratic Arlingtonians.

In the inner suburbs, where Democrats rule and where Sen. John F. Kerry last year became the first Democratic presidential candidate to carry Fairfax County in 40 years, education is the top issue. In his ads, Kaine accuses Kilgore of insufficient support for schools and touts a plan for expanding early childhood education.

Still, with an influential and established business community, burgeoning cultural and arts institutions, new college campuses and Tysons Corner eager to serve as "downtown," there is a growing sense of identity among the region's more than 2 million residents.

"I think even more so than ever in the past," said Sean T. Connaughton, the Republican chairman of the Prince William Board of County Supervisors. "And I think Northern Virginia is starting to have its own identity that is separate from Washington."

With its schools, wealth and highly educated workforce, Northern Virginia brings up the average and "makes the rest of the state look better than it is," said regional economist Stephen S. Fuller, a professor at George Mason University. "It's more important than its population would suggest, and it's more important than the number of votes it can cast."

The Money Divide

Gov. Mark R. Warner, the Democrat who four years ago became the first Northern Virginian to win the governor's office since Charles S. Robb in 1981, says that liberals in Alexandria and conservatives in eastern Loudoun share as many things as divide them.

"One thing would be that they all think of themselves as Northern Virginians," he said.

Most Northern Virginians were not born in the state; most other Virginians were. Many Northern Virginians share a sense of grievance at how much of their tax money goes to fund projects elsewhere in the state.

Craig Monroe, a Republican volunteer who spent an evening last week looking for Kilgore supporters among the winding roads and cul-de-sacs near Centreville High School, was making just that pitch. "Fairfax County educates 14 percent of the state's children but gets back only 7 percent" of the state's spending on education, he told his neighbors in the Little Rocky Run subdivision, where Halloween decorations are on display outside the neat houses and where campaign yard signs are forbidden until 30 days before the election.

Money is a major divide between Northern Virginia and the rest of the state, and that has political reverberations. According to the recent Washington Post poll, Northern Virginia residents, both inside and outside the Beltway, are more apt to say that the economy is in good shape than are residents of the rest of the state.

Northern Virginia has a third of the state's jobs but accounted for nearly three-quarters of the state's new ones this past fiscal year. Northern Virginia's economy is growing because of wages and salaries; the economy in the rest of the state is growing because of retirement checks, disability benefits and other fixed payments, Fuller said.

Most of the state's richest households -- with incomes of $100,000 or more -- are in Northern Virginia. So are most Virginians who hold the graduate or professional degrees that are the tickets to those higher incomes and a lure to employers.

Northern Virginia also is home to most of the state's immigrants and to most of the state's Asian and Hispanic residents. Its workforce has a somewhat higher share of government employees than the state overall, and a huge part of its economy depends on government contracting, which held down the region's losses during the recent recession.

"Government spending drives the region," said Rep. Thomas M. Davis III, a Fairfax Republican. "And because of that, a lot of the anti-government rhetoric you hear [in campaigns] has much less salience here."

Established Identities

Moran, the House Democratic Caucus chairman who represents liberal Alexandria, and Del. Richard H. Black, the hard-right Republican from Loudoun whose political survival has infuriated Democrats since 1998, agree on this: Northern Virginia is represented in Richmond by some of the most liberal, and some of the most conservative, legislators in the state.

"I'm not a social scientist," Moran said, "but it defies me to believe that issues and views 15 miles down the road can be so different."

Said Black: "If you asked, 'Where are the most conservative legislators in Virginia,' most people would probably think Southside or somewhere else downstate. But actually they are from this band of Republican-leaning areas in Loudoun, Prince William, western Fairfax and Fauquier."

Republicans delight in this statistic: Of the country's 100 fastest-growing counties, most of them exurbs, Bush in 2004 won 97, including all of those in Virginia.

The region's more established suburbs also have an established identity. Elizabeth Wakefield, a projects manager who lives near the Arlington-Fairfax border, is a lifelong Democrat who will be voting for Kaine. So, she thinks, will most of her neighbors. "There's definitely a Republican down the street, but we don't talk about it," she joked.

The fast-growing exurbs, with their new housing and open space, draw a greater share of married couples, who tend to be less liberal than single people. In Arlington and Alexandria, married couples make up a third of all households; in Prince William and Loudoun counties, they are nearly two-thirds. "They are more likely to be associated with the church. Because of the children, they are more concerned about the values issues," Black said.

The outer counties also have a higher share of whites, whose voting patterns are more conservative, than the inner counties.

"The Republicans, you could argue, are just moving" as the inner counties become more populated and urban, said Davis, who added that he regularly encounters his former constituents when he goes to Loudoun. "They are people who just want to live a suburban lifestyle, and they are willing to make the commute to do it."

Connaughton and some others think the legislative seats are anomalies to some extent, races driven more by political ideologies than other local contests.

There are also changes in the migration patterns, according to state Sen. William C. Mims (R), that could slowly change Loudoun's political climate. Its booming economy draws residents from all over the country, not just the inner suburbs. "Those people are less likely to be reliably conservative," he said.

Those changes have already taken place in Fairfax, the million-person, urban-suburban behemoth that is nearly twice as big as Prince William and Loudoun combined. As with other aging suburbs, Fairfax has taken on the trappings of a city, with more single people, immigrants, racial minorities, all living in a more densely populated place. Those demographic changes were one reason the county gave Kerry a nearly 35,000-vote advantage last year, strategists of both parties agree.

Davis said the region, taken as a whole, must be seen as "centrist," and others concur.

Robert Lang, director of the Metropolitan Center at Virginia Tech, said exurbs tend to reflect the region. The outer suburbs in Dallas and Atlanta are deeply conservative. The ones in New York and San Francisco are barely Republican.

The word he used for the Washington region is "contested."

Jerry Kilgore team members Alma Jackson of Fairfax, left, and Craig Monroe of Centreville go door-to-door in Centreville. Kilgore has more staff in Northern Virginia than anywhere outside his Richmond headquarters.