BOSTON -- At the stroke of midnight next Monday, the Commonwealth of Massachusetts will become the first state in the nation to begin processing marriage licenses to gay couples, an event so historic that even though it has not yet taken place, it already has sent shock waves across the country and spawned a frenzy of legislation.

Less than six months ago the Supreme Judicial Court of Massachusetts ruled that denying gay couples the "protections, benefits, and obligations of civil marriage" violated the tenets of equality embodied in the state constitution. Just three months ago, the court followed up by telling the state legislature that establishing civil unions, a parallel system of marital rights, would not satisfy the constitution because it would create an "inferior and discriminatory status for same-sex couples."

Since the Massachusetts court's first ruling, two-thirds of the nation's state legislatures have introduced legislation that would either bar the recognition of same-sex marriages in their states or encourage a federal constitutional amendment banning same-sex marriages, a proposal that is now before Congress and supported by President Bush.

"There was a sprinkling of this type of proposed legislation around the time of the passage of the civil union law in Vermont, but the bulk of the activity has happened since the Supreme Judicial Court ruling in November," said Christi Goodman, program manager for the National Conference of State Legislatures, a bipartisan group that tracks state legislation. "It's been changing so rapidly," she said, "it's been a full time job keeping up with it."

The legislation has met mixed success. While 23 states have introduced proposals to amend their constitutions to ban same-sex unions, 12 have failed, Goodman said. Five of the successful ones will be voted on in November, and two -- in Wisconsin and Massachusetts -- must be approved by their legislatures a second time before going to voters for approval.

National polling continues to show a majority of Americans opposed to gay marriage but disinclined to amend the federal constitution. The latest survey by the Annenberg Public Policy Center of the University of Pennsylvania showed that while 64 percent of Americans oppose legalizing gay marriage in their own states, only 41 percent favored amending the U.S. Constitution to say no state could allow it.

Support for a federal constitutional amendment has been growing, however, in the wake of the Massachusetts court ruling and gay marriages performed in San Francisco and New Paltz, N.Y., by rebellious municipal officials. ABCNews-Washington Post polling showed that around the time hundreds of same-sex couples were married in San Francisco, there appeared to be a backlash in the West. In surveys taken between January and February support for a federal constitutional ban on gay marriage rose to 46 percent from 38 percent.

The question nevertheless remains whether Americans will become more or less accepting of gay marriages once they become routine in Massachusetts.

Members of conservative groups staunchly opposed to gay marriage, such as Focus on the Family and the Family Research Council, believe the Massachusetts ceremonies will drive public opinion further against the legalization of homosexual unions.

"On any issue you have people on the left and the right, and everybody else in the middle," said Glenn T. Stanton, senior analyst for marriage and sexuality at Focus on the Family. "And I think a lot of those people are becoming polarized more against the idea of same-sex marriage. They understand that the way that all of us understand and define marriage is being dramatically changed forever and for everybody."

Tony Perkins, president of the Family Research Council, said members of his group and the other organizations that make up the Coalition for Marriage will be very visible in Massachusetts this month to raise public awareness about the legal and cultural changes taking place there.

"I really think that for the other side, this could backfire," Perkins said. "What's going to happen now is that this is going to move from an academic debate to a very real public policy crisis that should really cause concern around the country. I think people will soon begin to realize that this is not isolated to Massachusetts."

People on the other side of the issue, like Cheryl L. Andrews, a selectman in Provincetown, dismissed such views. Provincetown, with its large gay population, is among a handful of Massachusetts cities that will not turn away couples from other states when it begins processing marriage licenses on May 17, despite the strident objections of Republican Gov. Mitt Romney.

Andrews, who plans to apply for a marriage license with her own partner on May 17, believes once the marriages begin in Massachusetts, fears about same-sex unions will subside.

"As soon as people wake up and look at their partner and their wives and their kids and their wedding bands and go 'Oh wow, nothing's changed for me' just because somebody down the street married their gay partner, I think everything's going to be just fine," Andrews said.

Across Massachusetts, clerks in 351 towns and cities have been preparing to accept an onslaught of marriage license applications from gay couples on May 17. Formal training began last week after they protested that there hadn't been enough direction from the state.

Part of the delay was due to the whirlwind of attempts by Romney, gay marriage opponents and some state legislators to push back the court-ordered deadline.

After Massachusetts lawmakers passed a proposal to bar same-sex marriages in the state constitution -- which must be approved again next session and then by voters in 2006 to take effect -- Romney attempted to stay court ruling until the process takes its course. But his request was denied, and a string of legal challenges by conservative groups have thus far been unsuccessful, as well.

Romney also took steps to prevent out-of-state gay couples from getting married in Massachusetts. In March, he began heralding a 1913 law, once used to prevent interracial couples from marrying if their own states forbade it. Under this law, Romney said, out-of-state couples whose marriages would not be recognized in their own states could not be married in Massachusetts. This would include the 38 states that have adopted the federal Defense of Marriage Act.

Several Democratic senators filed legislation in April to repeal this law before the May 17 deadline. But then, just last week, the town clerks were told by Romney's legal counsel that they would not be required to ask for documentation proving residency because marriage license forms include a sworn statement that at least one member of the couple lives in the state or intends to.

So, with only seven days to go until gay marriages become legal in Massachusetts, much of the discretion has been turned over to the clerks. They will begin accepting applications May 17, but since licenses are granted only after a three-day waiting period, the first same-sex marriages will not take place until May 20.

The City of Cambridge announced it would begin processing licenses at midnight on May 17 and would mark the historic event with a wedding cake and sparkling cider.

"We wanted it to be a celebration," said Cambridge Mayor Michael A. Sullivan, who said the city is expecting at least a few hundred couples to apply that day. "This is a community that prides itself in diversity and diversity comes in a variety of aspects: it comes in race, it comes in national origin, it comes socio-economics, it comes in gender, and it comes in sexual orientation. So this is a piece of that diversity."

Officials in several cities, such as Provincetown and Worcester have said they will not turn away couples from other states, even though the "intention to marry" form states that they should at least intend to live in Massachusetts. Some opponents of gay marriage have suggested that flouting the spirit of this provision could spur legal action.

Linda E. Hutchenrider, president of the Massachusetts Town Clerk's Association and clerk of Barnstable, said most clerks will simply try to be consistent and stay within the law.

"Hopefully within a few weeks it's going to be a non-issue," she said, "and life can go back to normal."