Christopher G. Oprison, who is challenging a veteran GOP delegate for his House seat in Loudoun County, says he knows exactly what young couples are looking for in their quickly growing community. It begins with getting government "out of their pocketbook and off of their backs."

"The younger families here, with young children, they want a more conservative leadership," said Oprison, 34, a Washington lawyer who moved to the county in 2003. "It's clear that my opponent isn't so in touch with those values."

His opponent, six-term Del. Joe T. May, was among the 17 Republican delegates who defied the party leadership and helped push through the state tax increases last year. Six of the delegates are being challenged in primaries on Tuesday, based largely on their tax stand.

Oprison has proposed a tax relief amendment to the Virginia Constitution. It would return home assessments to the levels they were at two years before the amendment passed, then cap their assessment increases at 2 percent a year.

The plan also would prohibit local governments from raising the tax rate above $1 per $100 of assessed value.

"Our tax plan . . . helps everybody -- seniors, young families -- but it really helps those who are moving in here, who are buying homes," said Oprison, who lives in one of the thousands of new single-family homes that have been built recently in Washington's outer suburbs.

In the 2004 presidential election, 97 of America's 100 fastest-growing counties voted Republican, according to a study by the Los Angeles Times. Virginia has several such communities: Loudoun, Spotsylvania and Stafford counties are ranked in the top 25, according to federal statistics, and all voted overwhelmingly Republican in November.

Several of the GOP delegates who face anti-tax challengers represent these fast-growing areas.

The delegates and the challengers tend to have different visions of what the new residents want.

The challengers say that many of the new voters are looking for a more conservative brand of politician, one who takes a harder stand on taxes and social issues. Oprison, like many of the challengers, said such services as education and transportation can be funded by Virginia's future budget surpluses and reining in state spending.

May, first elected to the House of Delegates in 1993, has hit back hard against Oprison and his plan, saying the proposal would starve schools and public safety and encourage governments to approve more commercial development so they could replace real estate tax money with sales tax revenue. He said the plan indicates that Oprison does not understand the traditions and values of his new community at all.

"My opponent's proposal will absolutely decimate local governments and their ability to raise any money for these things that people care about," said May, 68, who has spent most of his adult life in Loudoun.

And in a county that is building five schools a year, May said Oprison's plan -- and his campaign -- fundamentally miss what is truly on the minds of many newcomers: They want good schools that are not crowded, enough recreational park facilities for the burgeoning number of children and transportation alternatives that get people to and from work quickly.

"What voters in this community are looking for is a good quality of life, where they know schools and transportation will be well funded," said May, an engineer.

May said that since 2003, 14,000 new voters -- representing a 20 percent increase -- have arrived in the 33rd House district, which encompasses parts of Loudoun and Clarke counties.

"I look at Prince William, Loudoun, Stafford, Spotsylvania -- they all tend to be . . . more conservative than the average Republican community," said Sen. Ken Cuccinelli (R), who represents a rapidly growing -- and increasingly conservative -- part of western Fairfax County. He has endorsed Oprison. "If that's indicative, you're not just talking about Republican growing communities, you're talking about growing conservative communities."

Other analysts and local officials said they doubt that the new voters are so conservative that that they would buy into the challengers' hard stances on taxes.

"The people who are moving into Loudoun . . . they may be Republican, but it's for a variety of different reasons," said John Davis, a veteran of Virginia politics who serves as a consultant to May's campaign. "Just because there are more Republicans out here doesn't mean they are coming out here for the same reasons."

Oprison has tried to characterize May as soft on core Republican values, hoping to stoke the district's conservative voters. May has touted his support from other state conservatives, including Jerry W. Kilgore, the likely Republican gubernatorial nominee, GOP leaders in the House of Delegates and Rep. Frank R. Wolf (R-Va.). And he said Oprison lacks roots in the community that he has spent a dozen years cultivating.

"New people do add a new dimension to the community," May said. "But there's a depth of Loudoun tradition and values that I think I understand very well."

As in the five other districts where the GOP mavericks face primaries, the incumbent in Loudoun has more money. Oprison had raised $75,153 as of June 1, according to the State Board of Elections, and May had raised $253,000.

Loudoun County's Christopher G. Oprison, right, who is challenging six-term Del. Joe T. May, speaks with John Long while campaigning in Leesburg.