NEW YORK, N.Y. (AP) — Despite laws on the books already barring gay marriage, legislators in at least eight states are pushing for new, more sweeping measures in hopes of preventing any ripple effect from laws and court rulings elsewhere.

In each case, Republican lawmakers in states with existing Defense of Marriage acts seek to go a step further, amending their constitutions to specify that marriage must be heterosexual. State Rep. Bill Graves, a bill sponsor in Oklahoma, wants to stipulate that same-sex unions are “repugnant to the public policy” of the state.

Supporters say the constitutional amendments are necessary to ensure that legislation and court judgments in other states — such as the recent ruling in favor of gay marriage by the Massachusetts Supreme Judicial Court — will not compel recognition of same-sex unions in their own states.

Gay-rights activists see the amendment campaign as vindictive and partisan.

“This is a political attack, motivated by fierce anti-gay opponents who want to slam us again and again,” said Evan Wolfson, executive director of the national advocacy group Freedom to Marry. “They are not just looking to suppress gay marriage, but to deny gay people any measure of legal protection and human dignity.”

In all, 37 states and the federal government have Defense of Marriage acts that say marriage can only be between a man and a woman.

Ohio may soon become the 38th state; its Senate approved one of the most far-reaching gay marriage bans in the country Wednesday, making only minor changes in a House-passed version. Going further than the laws in most states, Ohio’s bill also would prohibit state employees from getting benefits for domestic partners, whether gay or straight.

Proposed constitutional amendments that would ban gay marriage have been introduced in Arizona, Georgia, Virginia, Oklahoma, Kentucky and Michigan; one is expected soon in Alabama. An Idaho Republican, Rep. Henry Kulczyk, plans to introduce a similar measure there, to the dismay of some Democrats.

“We’ve got enough contention to deal with rather than going through a litmus test for the reactionary right,” said Senate Minority Leader Clint Stennett.

Massachusetts does not have a Defense of Marriage Act, but the high court ruling there has sparked vociferous public debate and an anti-gay marriage amendment has been proposed by its lawmakers as well.

The measure in Virginia has already advanced, winning unanimous support this week in the House Rules Committee.

“Marriage for 6,000 years has been defined a certain way,” said the amendment’s sponsor, Robert McConnell.

Georgia’s proposed amendment — which could go on the November general election ballot — was presented in the state Senate. Any change to traditional marriage “begins to tear at the foundations of our institutions,” said Senate Republican Leader Bill Stephens.

Gay-rights advocates and some Democratic lawmakers denounced the measure as politically motivated.

“The purpose of amendments is to create protections for the citizens of Georgia, not to write discrimination into the constitution,” said Allen Thornell, executive director of the gay-rights group Georgia Equality.

The American Friends Service Committee — a Quaker social justice group — joined the campaign against the proposed amendment in Michigan, urging people to e-mail their legislators. In Kentucky, about 30 gay-rights supporters protested at the state Capitol, many carrying signs saying, “Anti-marriage amendments hurt my family.”

Two Kentucky legislators who oppose the amendment are sponsoring a counterproposal that would outlaw discrimination against gays.

“There’s no excuse why fairness cannot be passed,” said Democratic Rep. Kathy Stein. “Other than the fact that, unfortunately, a number of my colleagues ... are afraid to think about it.”

Pending final resolution of the Massachusetts court ruling, no state allows full-fledged same-sex marriages. Vermont recognizes marriage-like civil unions, while California, Hawaii and New Jersey grant various rights to same-sex couples registered as domestic partners.

Legislators in Maryland and Colorado hope to get civil union legislation considered by their colleagues this session.

In his State of the Union speech, President George W. Bush indicated he would support an amendment to the U.S. Constitution that would limit marriage to a man and a woman. He suggested this option would be needed only if “activist judges” overruled existing federal and state Defense of Marriage laws.

If Ohio enacts its pending Defense of Marriage act as expected, only 12 states, including Massachusetts, would be without one.