Boston ? Gay rights supporters are training activists to become door-to-door campaigners. Conservatives are planning a legislative guide for voters.

Both sides already are gearing up for the fall legislative elections as they jockey for influence in the fight over a proposed constitutional amendment that would ban same-sex marriage.

After the state’s highest court said Massachusetts couldn’t ban such marriages, the Legislature adopted a proposed constitutional amendment that would ban them but also would legalize civil unions for gay couples.

It was adopted by only a four-vote margin, and lawmakers who will be elected this fall must pass it again — in the exact same form — during the 2005-06 legislative session before it can go to voters on the November 2006 ballots.

Advocates on both sides have started surveying voters, analyzing lawmakers’ records and recruiting candidates.

“We will be doing everything we can, knocking on doors, helping candidates get their signatures gathered, doing fund-raising,” said Michael Carl, president of The Heritage Alliance, a political action committee he formed to field candidates to run against legislators who support gay marriage.

“The issue of marriage is too fundamental to the cultural makeup to leave it to those who want to redefine it for their own reasons,” Carl said.

Last weekend, in the days leading up to the final phase of the legislature’s vote on the amendment, gay-rights activists trained volunteers as they fanned out through neighborhoods in metropolitan Boston.

“The gay and lesbian community was very politically disenfranchised and disengaged for the past few decades, but through the constitutional convention, they have realized that people can really make a difference if they speak out and get involved,” said Josh Friedes of the pro-gay marriage Freedom to Marry Coalition. “We are seeing an increase in the level of activism and that bodes well for the future.”

They got some strong reactions in the blue-collar East Boston neighborhood.

“I’m not interested in that (stuff). I’m 90 years old, I’m going to worry about that?” one man said before slamming the door.

But lifelong East Boston resident Victor Bono, 50, agreed to sign a form letter supporting the Supreme Judicial Court decision that legalized gay marriage, which will be sent to state Senate President Robert Travaglini, a Democrat from East Boston.

Bono said he understood that gays had “as much right to be happy as anyone else.”

The Coalition for Marriage, an umbrella group for organizations opposed to gay marriage, plans to reactivate phone banks that were used throughout the constitutional convention — which took place intermittently over the past two months — to urge residents to contact their lawmakers and lobby against homosexual marriage.

A conservative group, the Massachusetts Family Institute, has said it will develop its first voter guide listing candidates’ positions on gay marriage and other social issues.

“We are hopeful that we will be able to keep people informed and energized to work in the political process as they did in the legislative process,” said Ron Crews, the organization’s leader, who plans to work for both Republicans and Democrats who oppose gay marriage.