Several political scientists who have studied state ballot measures said the polling data from Virginia appeared to defy expectations, given the commonwealth's reputation as a conservative state. "This is quite a surprise," said Daniel A. Smith, an associate professor of political science at the University of Florida. "In an ostensibly conservative state like Virginia, you'd expect to see the numbers up around 60 or 70 percent."

The lower numbers in Virginia reflect a national trend of weakening support for state efforts to ban same-sex marriage, several experts said. Twenty states have passed similar measures since 1998, many with about 75 percent support. The lowest level of support an amendment received was 57 percent in Oregon in 2004. But this year, poll results in several states with similar ballot measures show weaker support than in 2004, when 11 states passed constitutional amendments. Polls in Colorado and Wisconsin show results similar to Virginia's; poll results in South Dakota are mixed.

The only group to significantly cross party lines was blacks. In the poll, blacks supported Webb by 81 percent to 11 percent, but they favored the amendment 61 percent to 34 percent. "I don't believe in gay relationships; I just don't believe that they are right," said Aaron Moore, 26, from Chesapeake, who added that he follows the Pentecostal faith and will vote for Webb. "Even though I'm a Democrat, it's just something that I disagree with most Democrats on."

"I'm not a homophobe," said Charles Wortham, 60, a dentist from Hanover County, outside Richmond. "My view is simply that marriage is there to establish a legal process for the procreation of children. It's Mother Nature. Same-sex couples can't naturally reproduce, so it doesn't seem like they should be able to marry like a traditional family."