Boston ? Boisterous opponents of same-sex marriage sang, cheered and chanted Sunday at a rally to build support for a state constitutional amendment defining marriage as between one man and one woman.

The demonstration on the Boston Common, a short distance from the Massachusetts Statehouse, broke out into chants of “Let the people vote!” while demonstrators held aloft banners with phrases such as “Marriage, ancient, sacred,” and “Repent or perish.” Police estimated the crowd at 2,000 people.

Archbishop Sean O’Malley of the Roman Catholic Archdiocese of Boston said the rally was not about “hatemongering,” as some critics have charged.

“We are here because we are concerned about marriage and about family,” he told the cheering crowd. “Good strong marriage and family are good for our country, for society.”

Massachusetts’ highest court, the Supreme Judicial Court, ruled 4-3 in November that same-sex couples had a right under the state constitution to the benefits of marriage. This past week it ruled by the same ratio that only marriage — not civil union — would satisfy its initial decision.

The court gave the Legislature a mid-May deadline to comply with its ruling. Legislators, meanwhile, are meeting Wednesday for a constitutional convention to consider an amendment banning gay marriage, but 2006 is the soonest voters could approve such an amendment.

During the rally, several hundred supporters of gay marriage demonstrated loudly at the Episcopal Cathedral Church of St. Paul across the street.

A poll released Sunday by Merrimack College’s Center for Public Opinion Research suggested that support for gay marriage might be slipping, and support for legalizing civil unions growing.

Joe Modugno, right, of Milton, Mass., holds a rainbow flag during a rally to support same-sex marriage across the street from the Boston Common. Hundreds of people opposed to same-sex marriage gathered Sunday to show support for a constitutional amendment that would define marriage as the union of one man and one woman.

Of 501 adults interviewed by phone in late January and early February, 33 percent said the state should recognize gay marriages, compared with 37 percent in November. In the latest poll, 43 percent said the state should recognize civil unions, compared with 38 percent in November. The margin of error was 4.5 percentage points.

Andrew Curry holds a cross during a Boston rally to protest same-sex marriages. Archbishop Sean O'Malley of the Roman Catholic Archdiocese of Boston was among attendees Sunday.