Proposition A, the sweeping growth-control initiative, was rejected overwhelmingly by San Diego County voters Tuesday.

The measure was trailing by a 64 percent to 36 percent margin, with 62 percent of precincts reporting.

"It looks like those numbers are holding up," said Eric Larson, executive director for the San Diego County Farm Bureau, which led the fight to defeat the measure. "We feel very good about that. I have to admit, the numbers are better than we expected."

Also celebrating Tuesday night was Matt Adams, spokesman for the Building Industry Association of San Diego County.

"The demise of Prop. A is a victory for planning," Adams said. "It was dumb growth to begin with, and the voters recognized that."

Proposed by the conservation group Save Our Forest and Ranchlands, the measure was similar to an initiative promoted by the group in 1998 that went down in flames by a three-to-two margin. The group was outspent then, but this time it matched the opposition roughly dollar for dollar in the campaign to saturate airwaves and mailboxes with advertising.

"It's been a campaign of deceit (on the part of opponents)," said Eric Bowlby, spokesman for the Sierra Club, which endorsed the measure. "They stole our message to confuse the voters. They ran commercials saying that this would result in sprawl."

Also known as the Rural Lands Initiative, the measure would have strictly limited suburban-style housing for two decades on 700,000 acres -- a third of the county's unincorporated area. Those lands would have been blanketed with minimum lot sizes of 40, 80 and 160 acres. Changes to allow construction on those lands would have required a countywide vote.

Measure backers -- mostly environmentalists, labor unions and health-advocacy groups -- said suburban housing tracts did not belong in those backcountry areas. They maintained the measure was crucial to the region's future because it would have preserved large swaths of the rustic, oak-carpeted backcountry through 2023 and halt urban sprawl.

But farmers, home builders and landowners opposed to the initiative argued it would have aggravated a regional housing shortage that is driving up prices and spurring the local work force to live in Riverside and Imperial counties.

According to San Diego County planners, the net effect would have have been 6,000 fewer houses built in the unincorporated area of the county over the next quarter-century. That might sound like a lot, but the figure is equal to just 6 percent of the regional housing shortage.

The San Diego Association of Governments, a planning agency, says the region will add 900,000 people by 2030 and will need 400,000 new houses for them -- 100,000 more than planned by cities.

In light of a 100,000-home shortfall, 6,000 fewer units under Prop. A would have been inconsequential, said affordable-housing experts. And measure proponents said the county could easily make up that difference by allowing more growth in unincorporated towns, where there is plenty of room.

Proponents said the measure would have provided much-needed protection for watersheds and crucial habitat for rare animals in a county that is home to more endangered species than any other in the United States. Opponents maintained that national forests, state parks and environmental preserves already provide enough protection.

Backers also suggested the measure would have moved home construction out of backcountry areas ill-equipped to handle traffic, let alone provide urban services, and into the 18 cities that were designed for that purpose. But opponents said the measure would have derailed county planners' efforts to shift home building from the backcountry to unincorporated towns that also are equipped to provide urban-style services and could play a role in plugging the housing shortage.

According to a county analysis, there is little difference in how many people could move to the unincorporated area under the initiative and under the county's unfinished growth blueprint.

Called General Plan 2020 and scheduled for completion in 2005, that blueprint would let the unincorporated population grow from 443,000 today to 669,000. The initiative would allow the population to reach 650,000.

Contact staff writer Dave Downey at (760) 740-3529 or ddowney@nctimes.com.