RICHMOND -- A majority of Virginians support a proposed state constitutional amendment prohibiting same-sex marriages and civil unions, but a new poll indicates that opposition continues to grow as the Nov. 7 election approaches.

The amendment has the support of 52 percent of the registered voters who participated in a survey conducted by Mason-Dixon Polling & Research for The Roanoke Times and other state newspapers. According to the poll, 42 percent oppose the amendment and 6 percent are undecided.

The survey reveals stark differences of opinion between voters in densely populated Northern Virginia and the rest of the state. A solid majority of Northern Virginia voters now oppose the amendment, which still has strong support in every other region of the state. Support for the measure is strongest in the Roanoke Valley and Southwest Virginia, where 63 percent favor the amendment.

The results come from a telephone survey of 625 registered voters conducted from Oct. 17 through Thursday. The poll has a margin of error of plus or minus 4 percentage points.

The proposed amendment defines marriage as the union of one man and one woman. It also prohibits legal recognition of relationships between unmarried individuals that "approximate marriage" or partnerships that have the same rights and benefits as marriage.

Supporters of the measure argue that the amendment is needed to protect Virginia's ban on same-sex marriages from court challenges. Opponents argue that it would enshrine discrimination into the state constitution and reach beyond marriage to prohibit a variety of legal arrangements between unmarried heterosexual partners.

Opinions about the ballot question also break sharply along partisan lines, according to the poll. Republican voters favor the amendment by a margin of 76 percent to 20 percent, while Democratic voters oppose it by a margin of 64 percent to 28 percent. Independent voters are more divided, with 49 percent supporting the amendment and 45 percent opposing it.

The partisan split is also evident among statewide political figures. U.S. Sen. George Allen, a Republican seeking re-election, supports the amendment, and his Democratic challenger, James Webb, opposes it. The ballot question also has created friction between Gov. Tim Kaine, a Democrat, and the Republicans who occupy the state's other executive branch offices.

Kaine reiterated his opposition to the amendment Tuesday by holding a press conference with his wife, Anne Holton, and Holton's parents, former Gov. Linwood Holton and Jinks Holton.

Kaine became the 200^th lawyer to sign onto a legal review committee created by The Commonwealth Coalition, which is organizing opposition to the amendment. Kaine said the second and third sentences of the proposed amendment are so vaguely constructed that they could have "unintended consequences" on a variety of legal rights now available to unmarried individuals, regardless of sexual orientation.

"The constitution shouldn't include language taking away rights in vague or unnecessary ways," Kaine said.

Kaine's comments drew swift responses from Lt. Gov. Bill Bolling and Attorney General Bob McDonnell, who support the constitutional change. McDonnell, who issued a formal opinion in support of the amendment last month, called Kaine's comments about unintended consequences "completely wrong and legally unsupportable."

"The proposed amendment preserves marriage as a union solely between one man and one woman, while not limiting or infringing upon the current legal or civil rights of unmarried Virginians," McDonnell said.

Bolling issued a statement supporting McDonnell's opinion and accusing Kaine of breaking a 2005 campaign promise to support the marriage amendment. Kaine said Tuesday that he would have supported the amendment if it merely defined marriage.

"I am very disappointed that Governor Kaine has let the people of Virginia down on this important issue," Bolling said.

Kaine did have a prominent Republican in his corner Tuesday -- his father-in-law. Linwood Holton, the first Republican governor of Virginia during the 20^th century, said the proposed amendment "runs a serious risk of messing up our constitution."

"We're talking in this amendment about fooling around with that very basic document in a way that will create confusion and, unfortunately, litigation for two or three generations," said Holton, who practiced law in Roanoke before his 1969 election as governor.

Anne Holton, a former Richmond juvenile and domestic relations judge, said the amendment's "ridiculously broad and vague" language could undermine domestic violence laws and affect child custody rights of unmarried adults, among other things.

"I feel passionately about the value of strong marriage, but it is false advertising to say that this is a pro-marriage amendment," the first lady said. "It does absolutely nothing to protect and strengthen marriage."

She also questioned the political motivation behind the amendment, though she said: "I don't think that the vast majority of the people who plan to support it mean it as a hateful thing."

"But I do worry that some of the origin of it is the politics of exclusion and the politics of separating out those who we're different from rather than trying to reach out with empathy and understanding," she said.