As political pundits sifted through the results of Tuesday's gubernatorial election, they found a surprise: Gov.-elect Timothy M. Kaine, a Democrat, won Northern Virginia's two rapidly growing outer counties, Prince William and Loudoun, long considered to be reliably Republican.

A closer look at the results in Prince William reveals another surprise: Kaine not only won the county by almost 2 percentage points, but he did so by making significant gains in its booming western half -- areas that campaign strategists from both parties have considered the reddest part of a red county.

"We weren't racking up the margins we needed in the Bull Run-Linton Hall area," Brian Murphy, chairman of the Prince William County Republican Committee, said of precincts where dozens of new communities have been built in the past decade, and where Republican Jerry W. Kilgore was expected to win big. "In the areas where Kilgore should have been making up ground, he tied."

In the Bull Run precinct, for instance, where President Bush won 65 percent of the vote last year, Kilgore won with 55 percent Tuesday. In the Linton Hall precinct, where Bush won 61 percent, Kilgore managed 55 percent. A similar pattern was repeated across the fastest-growing areas of Prince William.

In general, Kaine also did far better than Gov. Mark R. Warner (D) four years ago, a trend that some Republican politicians said they fear will continue unless the party changes course.

The reasons are varied, and involve changing demographics, how Kilgore and Kaine ran their campaigns and, to some extent, Bush's plummeting popularity, some say.

Diana Clemente of Haymarket, an independent who said she voted for Bush twice, voted for Kaine because she was simply "sick of the Republicans," she said.

"I'm disgusted with the deficit . . . and disturbed by the direction of the country," said Clemente, 37, who is a vice president of a technology company. "That's what decided my vote."

If some Democrats have held up the Virginia elections as the first signs of a voter revolt against an administration in trouble, Murphy and others said the shift in western Prince William had more to do with the individual candidates than the national climate.

"Kilgore had some ideas on transportation, but they weren't exactly great ones," Murphy said. "He certainly never brought them home as part of a bigger message."

Indeed, Kaine's positions on transportation came through to voters such as Robert Parker, a mortgage loan officer who recently moved from New York to Bristow and considers himself an independent.

"Overall, for me, it was Kaine's promises to improve transportation" and ease traffic, said Parker, 44, who said he was surprised that Northern Virginia's traffic was even worse than Long Island's, which is notoriously bad.

Many voters who might have leaned toward Kilgore, on the other hand, said they were turned off by his ads attacking Kaine's personal opposition to the death penalty, as well as Kaine's attacking his opponent's stand on abortion.

"They acted like a couple of school kids," said Patty Lugiano, 40, a computer saleswoman from Nokesville who considers herself Republican but who stayed home Tuesday.

Turnout was about 38 percent in the western precincts, lower than in the presidential election. With voters such as Lugiano sitting this one out, it seems that Kaine benefited, Murphy said.

"I'd like to say [the election] is a bellwether of positive things to come for Democratic Party in western Prince William County," said Rick Coplen, chairman of the Prince William Democratic Committee. "The Republicans and Jerry Kilgore focused on illegal immigration, the death penalty, abortion and quite frankly, those are important issues but they're not as important to peoples' everyday lives as transportation, health care, education. Those are the things that matter most."

Board of County Supervisors Chairman Sean T. Connaughton (R) said he agrees. The election returns from the western part of the county represent a broader trend that he expects will continue unless Republicans change their focus, he said.

"We are seeing a large influx of middle-class folks who are affluent and well-educated and are politically independent," Connaughton said. "Even though they may lean Republican or Democrat, they will vote for who they think is the best candidate. That means the party has to get back to its roots . . . focusing on issues such as transportation, education and public safety and the quality of life these people are expecting."

Gov.-elect Timothy M. Kaine (D) not only won Prince William County, but he did so by making significant gains in its fast-growing western half .