BOSTON — Democratic leaders are putting intense pressure on Massachusetts lawmakers to keep voters from deciding a proposed marriage protection amendment that carries national significance.

The Massachusetts Marriage Amendment defines marriage as the union of one man and one woman. It passed two required votes in the state legislature earlier this year. It needs another legislative vote at the next Constitutional Convention. If adopted by at least 50 of the 200 legislators this time, the amendment would go on the statewide ballot for all citizens to consider in November 2008.

The measure could end the state’s distinction of being the only one that allows same-sex “marriage,” and is poised to export it to others.

“Unfortunately, the political leadership is willing to go to the mat to deny people the right of due process,” said Lisa Barstow, spokeswoman for VoteOnMarriage.org, the coalition backing the amendment.

A June 14 legislative showdown is looming.

Because defenders of marriage believe they will prevail with 57 votes, opponents are pressuring lawmakers to switch votes. “We can’t afford to lose here,” said Arline Isaacson of the Gay and Lesbian Political Caucus.

A May 17 Boston Globe article suggested that support for the amendment is waning.

“Nothing could be further from the truth,” said Kris Mineau, president of the Massachusetts Family Institute, which is spearheading VoteOnMarriage.org.

The Globe reported that Democratic Party chairman Howard Dean offered to join the fray against the measure. The article’s headline announced: “Legislative Support Slim for Same-Sex Marriage Ban,” but gave only anonymous sources and activists’ claims to substantiate this.

Mineau said “there’s been a sudden influx of $750,000 overnight to conduct a four-week, all-out media blitz against us.”

The public relations campaign will feature pricey 30-second television slots run by the activist group MassEquality, which also has at least 14 full-time paid lobbyists working against the amendment. Spokesman Marc Solomon said the ads will argue that marriage is a civil rights issue that should not be subject to a popular vote.

Dan Avila, policy director for the Massachusetts Catholic Conference, countered that claim.

“It’s not true that ‘civil rights are not to be put to a vote,’” said Avila. “Every time we vote on a ballot question, we affect someone’s rights under civil law.”

Says the amendment: “When recognizing marriages entered into after the adoption of this amendment by the people, the Commonwealth and its political subdivisions shall define marriage only as the union of one man and one woman.”

In 2003, Cardinal Joseph Ratzinger, who is now Pope Benedict XVI, wrote: “The Church teaches that respect for homosexual persons cannot lead in any way to approval of homosexual behavior or to legal recognition of homosexual unions. The common good requires that laws recognize, promote and protect marriage as the basis of the family, the primary unit of society. Legal recognition of homosexual unions or placing them on the same level as marriage would mean not only the approval of deviant behavior, with the consequence of making it a model in present-day society, but would also obscure basic values which belong to the common inheritance of humanity. The Church cannot fail to defend these values, for the good of men and women and for the good of society itself” (Considerations Regarding Proposals To Give Legal Recognition To Unions Between Homosexual Persons, No. 11).

Coercion

The proposed amendment has already withstood a 2006 challenge to its legality. However, this did not stop Attorney General Martha Coakley in May from terming it “hate” and vowing to challenge it again should it succeed.

Lawmakers who support the amendment “are under incredible pressure to cave in,” Boston Cardinal Sean O’Malley said May 11 on his blog (CardinalSeansBlog.com). “Right now, people are not talking about what is at stake,” the cardinal said, but rather “reducing a very important human issue to political slogans and coercion.”

Gov. Deval Patrick has made no secret of coercing lawmakers to kill the measure, even if it means they would deny citizens the right to amend the constitution by refusing to address the petition.

He also intends to repeal a law that prohibits out-of-state couples from marrying if they would be ineligible to wed in their own state. Patrick said he wants to keep the measure off the ballot “rather than turn Massachusetts into a political circus for a national debate over something which is largely settled here.”

However, a record-breaking 170,000 signatures were collected in 2005 in support of the amendment. All four Massachusetts bishops signed a letter which they sent to each legislator. It noted that a recent Suffolk University poll showed that two-thirds of registered Massachusetts voters want action on the amendment.

The bishops have regularly urged people to remind lawmakers that voters have been denied a say in this debate.

A 2003 ruling by the state Supreme Judicial Court paved the way for marriage licenses to be issued to same-sex couples, but the Legislature never actually changed the marriage statute to legalize same-sex “marriages.” A bill filed by the homosexual “marriage” lobby and now pending seeks to do this if the amendment fails.

Meanwhile in New York, Gov. Eliot Spitzer recently introduced legislation that would eliminate gender from the legal definition of marriage. In Connecticut, the state Supreme Court May 14 heard oral arguments in a case seeking to legalize same-sex “marriage.”

Intense Prayer

With the help of the Boston-based lay political action group Catholic Citizenship, the Diocese of Fall River has undertaken a prayer drive for God’s protection on marriage. Father Samuel Leonard, the group’s spiritual adviser, asked for special Masses and hours of Eucharistic adoration. He encouraged Catholics to offer sacrifices and “intercede with God for his divine intervention and that his good will is accomplished.”

Bea Martins, a Catholic Citizenship lay leader, said, “We’ll continue to focus on prayer, because this will be won only with God’s help.”

Gail Besse writes from Boston.