It seems a can’t-lose proposition: Ask voters to ban same-sex marriages and they consistently endorse the idea, from the South to the West.

Kansas on Tuesday became the latest and 18th state to pass a constitutional amendment barring gay marriage. With conservatives pushing to define marriage as between a man and woman throughout the country, similar proposals are on the ballot in three other states next year and more than a dozen are considering them.

New England has been the major holdout. There, legislators and judges have strengthened rights for gays and lesbians. The Connecticut Senate on Wednesday voted to legalize civil unions. If the bill becomes law, Connecticut would be the only state to do so without a court order demanding lawmakers act.

Kansas voted by a more than 2-to-1 margin Tuesday to ban gay marriages and civil unions, and voters also ousted the lone gay city council member in Topeka, Tiffany Muller, who had defeated an emphatically anti-gay opponent in the primary.

The New England examples – most decisively Vermont’s civil unions and Massachusetts’ legalized gay marriages – are seen by ban supporters as the threat that’s helping their cause. Advocates for gay marriage also see those examples as a plus, by proving that fears gay marriage will somehow destroy society’s social fabric are unfounded.

“Massachusetts, the last time I checked … is still there. Marriage is still there,” said Joe Solmonese, president of Human Rights Campaign, a gay rights lobbying group. “People are going on with their lives, gay and lesbian couples are raising their families and living their lives like everyone else. None of what has been forecasted or what we’ve been warned about seems to have happened there.”

Connecticut offers the strongest recent pro-gay legislation by extending all rights and privileges of marriage to same-sex couples but without an actual marriage license.

In Maine, a new law signed last month protects gays and lesbians from discrimination, though it made clear it doesn’t extend the rights of marriage. The state already allows for domestic partners, who could be homosexual or heterosexual, many of the legal rights of marriage, such as rights to inheritance and benefits.

New Hampshire set up a commission to study civil unions.