BOSTON (AP) – When Gov. Mitt Romney leaves office in January for an expected bid for the 2008 Republican presidential nomination, opponents of same-sex marriage back home will lose one of their loudest cheerleaders.

Despite Romney’s departure, gay and lesbian advocates in Massachusetts – the only state to recognize same-sex marriages – aren’t taking anything for granted.

Worried their legal right to marry could slip away, activists are ramping up their efforts to mobilize sympathetic voters for the gubernatorial campaign.

In the first statewide race since same-sex marriage became legal, the issue, gay advocates say, remains polarizing, but the conversation has changed. It’s no longer about legalizing the unions anymore, but whether to revoke an existing right.

“All the Democrats now say gay marriage is OK and the law is the law,” said Arline Isaacson, co-chair of the Massachusetts Gay & Lesbian Political Caucus. “But just as importantly, maybe more importantly, do they support repealing it? Do they support letting it go to the gauntlet where it could be repealed? And are they going to stick to their word?”

Two days after the November election, lawmakers are due to vote on whether a constitutional amendment to ban same-sex marriage should be put to voters. If the amendment is approved by a quarter of the legislature this year and next, it will be placed on the ballot in November 2008.

“We don’t know what’s going to happen Nov. 9,” Isaacson said. “It’s entirely possible this petition will die. However, if it doesn’t it will then be voted on in 2007 again and having the right governor in place can make all the difference in the world.”

Kristian Mineau, president of the Massachusetts Family Institute, which is pushing the amendment, said he hopes whoever is elected governor will support the idea that the question should go before voters in 2008 – especially since backers collected more than the required number of signatures.

“There are several candidates out there who oppose us on the issue of the definition of marriage but agree on the constitutional process and that’s all that we’re asking for,” he said.

The same-sex marriage debate galvanized gays and lesbians to get involved in politics more than ever in 2004, and some analysts say they could prove to be an important voting bloc in this year’s primary and general election. Advocates noted that two years ago, every lawmaker who supported same-sex marriage and faced a same-sex marriage opponent won re-election.

“We realized in 2003 and early in 2004 that we would never be able to preserve marriage equality if we didn’t make everyone believe it was not a career-ending vote, so we put everything into the legislative elections. The results have been strong…. There is a lot riding on this election,” said Marc Solomon, the campaign director for MassEquality.

The only candidate who opposes same-sex marriage is Republican Kerry Healey. She said she supports the constitutional amendment but would file legislation to allow civil unions if it was approved by voters.

All three Democrats support same-sex marriage but are fuzzier on the question of whether they think lawmakers should block the proposed amendment from reaching the 2008 ballot.

Tom Reilly says he would vote against the amendment if he were a lawmaker but won’t say if the legislature should block it; Chris Gabrieli says he would work to defeat the amendment if lawmakers send it to the ballot but also won’t say whether lawmakers should block the amendment; and Deval Patrick says he hopes lawmakers find a way to avoid a vote on the question.

Patrick has garnered several high-profile endorsements from the gay community, recently winning the support of the Massachusetts Gay & Lesbian Political Caucus. In February, the 12,000-member Freedom to Marry Coalition endorsed him, citing his work on civil rights as a former Justice Department lawyer in the Clinton administration.

He also has the backing of many openly gay politicians, including U.S. Rep. Barney Frank, D-Mass., state Sen. Jarrett T. Barrios, D-Cambridge, and Kenneth Reeves, the first openly gay black mayor of Cambridge.

Gabrieli has received support from gays and lesbians who cite his early backing of same-sex marriage in 2002, when he ran for lieutenant governor.

Reilly initially opposed same-sex marriage, but later became a supporter, saying he had seen that the same-sex unions that have taken place since May 2004 haven’t hurt Massachusetts.

Reilly irked many gays and lesbians for using a 1913 law to block out-of-state same-sex couples from marrying in Massachusetts and for certifying the proposed amendment that would define marriage as a union of a man and woman. Reilly has said he disagrees with the ballot measure, but was upholding his duties as attorney general.

“Tom has been very clear that he is opposed to the ballot measure. If he were a legislator he would vote against it. If it does get to the ballot he will lead the fight against it.” Reilly’s spokesperson Corey Welford said.