Leaders of the McLean Citizens Association sat stoically unconvinced.

The civic group was being lobbied at a community center Tuesday night by representatives of Tysons Corner Center, the capital region's largest mall, who were seeking support for their proposal to ring the retailing behemoth with office and condominium towers. As watercolor images of stylish mid-rises flashed on a screen, the mall's attorney extolled the plan as "spectacular."

But neither the pictures nor the rhetoric seemed to move the audience, which numbered about 30. The group interrupted the presentation more than a dozen times with no-nonsense questions that betrayed a familiarity with planners' argot. There were references to "floor-area ratio," parking requirements and the comprehensive plan. At least a few times, the statements verged on hostile.

"We're not that naive," Susan Turner, association president, told attorney Antonio J. Calabrese, in disputing the project's tax benefits. "Please don't use that [figure] again."

As Fairfax County politicians, developers and business leaders push to transform the Tysons Corner area into a more traditional downtown, dozens of such meetings with well-organized civic groups, many of them experienced in sparring with developers, are likely to play a critical role.

To win approval for large-scale projects, county leaders often require developers to seek the favor of surrounding communities, an approach that amounts to the developer engaging in something like a political campaign.

It is unclear whether developers can create a traditional downtown at Tysons Corner, as county leaders want, while also heeding neighborhood demands.

But the mall representatives, whose proposal is one of the first to move to capitalize on the anticipated arrival of Metrorail to Tysons, are trying to shape public opinion in advance of county hearings planned for October.

They have prepared a Web site, www.tysonsfuture.com, to tout the project; donated $10,000 in April to the campaign fund of Fairfax Board Chairman Gerald E. Connolly (D); and set up meetings with condominium associations and other neighborhood groups.

The McLean Citizens Association was the third such meeting. The project would increase the amount of floor space on the property to more than 5 million square feet -- more than twice as much as in the Empire State Building.

"I expected to be on the hot seat," Calabrese said afterward, shrugging off some of the tough moments. "It was a healthy repartee."

Since 1994, the county land plan has called for creating a "downtown" at Tysons Corner, the capital region's second-largest job center, and as the rail plan advances, many developers have proposed bigger, more urban projects.

The political fate of this urbanization move will turn in part on the opinions of the numerous neighborhood groups in Fairfax, of which the McLean Citizens Association is one of the oldest and best organized.

Although the fundamental political unit in older cities is the ward or the precinct, in Fairfax County, it is the homeowners association, and there are roughly 2,000 of them.

Several elected leaders, including Connolly, launched their political careers in such associations, and they are often given significant clout in the county's development decisions.

When developers have sought his vote in a zoning case, Connolly has advised them to "show me the witch's broom" -- as the Wizard of Oz required of Dorothy -- meaning the developers must demonstrate that they have addressed neighborhood concerns.

"It's a way of ensuring that developers feel obligated to enter into a dialogue with the community," Connolly said. "We don't do land use by plebiscite. [But] we try to let people vent. We try to get them engaged."

Anti-development pressure from homeowner groups and other organizations already has made a significant mark on the suburbs: More than half of the land surrounding the nation's capital is now protected from typical suburban housing development, according to The Washington Post's review of land plans in 14 counties in Virginia and Maryland.

Some argue that catering to not-in-my-back-yard concerns can lead to decisions that sacrifice the greater good of the region. These neighborhood organizations have run afoul of environmental groups that often support dense developments as an antidote to sprawl.

"It's very frustrating," said Roger Diedrich, chairman of the Sierra Club's Virginia chapter, who lives in Fairfax. "It's natural for people to look at things from close to home. I think we're just looking at things from a broader perspective."

The effects of the Tysons Corner Center plan on traffic dominated Tuesday's discussion, and audience members, many of whom have at least some familiarity with the intricacies of traffic planning, dived in on both sides.

Boosters of the mall project, which would roughly double the amount of building on the property, argued that it represents a "smart growth" approach that would alleviate the road tie-ups by focusing development around a planned train stop and by building homes and offices in close proximity.

"People act like this plan has no rational basis for it," McLean Citizens Association member Dan Alcorn said. "That's not true."

But others questioned how adding development in Tysons Corner could reduce its traffic troubles.

"Whatever [traffic] you add to a disaster will become an even greater disaster," said retired economist Robin Bates.

Jim Robertson, chairman of the association's planning and zoning committee, sees the civic group as far from omnipotent, though it can often extract concessions from developers. He defended its role.

"They may think we're hard-nosed," he said. "But we're the ones who have to live here and drive around every day."

Representatives from Tysons Corner Center outlined a proposal to surround the megamall with condominium and office towers. Jim Robertson of the McLean Citizens Association thanks attendees. In Fairfax County, it is common for citizens groups to have input on development. Residents did not hesitate to challenge the proposal. "We're not that naive," Susan Turner, president of the McLean Citizens Association, said in response to statements about the plan's potential tax benefits. Antonio Calabrese, an attorney working on the Tysons Corner Center proposal, details the plan to the audience at the meeting arranged by the McLean Citizens Association, the third such gathering developers have attended. Robin Bates, a retired economist and area resident, voiced concerns at the meeting about the project exacerbating gridlock. "Whatever [traffic] you add to a disaster will become an even greater disaster," he said.