Reporting from Washington — Two years ago, a small and little-known civil rights group in Boston launched a legal attack on the federal Defense of Marriage Act, which defines marriage as a legal union between a man and woman. But it did not argue that gays and lesbians have a right to marry under the Constitution.
Instead its strategy was to take smaller steps first and focus on a narrower argument: that it is unconstitutional to discriminate against legally married gay couples.
INTERACTIVE MAP: Track rights for same-sex couples
Well aware that fundamental change in the law comes slowly, the group has followed the model of incremental wins laid out by Thurgood Marshall's attack on racial segregation in the 1950s and Ruth Bader Ginsburg's campaign against sex discrimination in the 1970s.
In its quest to legalize gay marriage, the group, Gay & Lesbian Advocates & Defenders, sought to win rulings to establish the civil rights principle that discrimination based on a person's sexual orientation violates the Constitution's guarantee of equal protection under the law.
After a federal District Court in Boston struck down the Defense of Marriage Act last year and the Obama administration announced last week that it would no longer defend it, the Boston group has a clear pathway to the Supreme Court that would allow the justices to rule in favor of equal rights for gay couples without facing the much broader question of whether all the states must authorize same-sex marriages.
That targeted approach has a much better chance of winning the crucial vote of Justice Anthony M. Kennedy. He has twice written strong opinions that favored gay rights, but neither had a wide impact. In 2003, he spoke for the court in striking down the handful of remaining state laws that criminalized private sex between gays.
But many who know Kennedy believe he would be wary of joining a ruling that mandated the right to same-sex marriage nationwide. The justices now on the court arrived after the Roe vs. Wade ruling in 1973, and they say the court moved too far too fast by legalizing abortion nationwide in a single decision.
Currently, only five states authorize same-sex marriage. And while public opinion has been shifting steadily in favor of gay rights, most polls continue to show a slight majority opposed to same-sex marriage.
Mary Bonauto, civil rights project director for GLAD, said the Boston group's lawsuits on behalf of gay couples focus on the principle of equal treatment under the law.
"The federal government doesn't marry people. States decide on marriage," she said. "We are asking, 'Why can the federal government treat one group of married people differently from another?' "
Their lead plaintiff, Nancy Gill, is a 53-year-old postal worker who wants to add her spouse to her health insurance plan. The two have been together for 30 years and are raising two teenagers.
The suits filed by GLAD speak for more than a dozen other couples in Massachusetts and Connecticut, as well as for several widows and widowers. Their clients' problems involve matters such as Social Security benefits for spouses, tax deductions for married couples and inheritance tax policies that benefit married couples.
Under the Defense of Marriage Act, federal agencies may not recognize a same-sex marriage as legal, even if it is legal in the state.
Last year, District Judge Joseph Tauro, a 79-year-old President Nixon appointee, said he saw no reasonable basis for upholding such discrimination. Atty. Gen. Eric H. Holder Jr. came to the same conclusion last week, saying there were no "reasonable arguments" that would justify such discrimination by the government.
No one is predicting a quick resolution.
Thurgood Marshall, a lawyer for the NAACP Legal Defense Fund before he became the nation's first black Supreme Court justice, brought civil rights cases for two decades before he won the historic high court ruling that struck down racial segregation.
He sued first on behalf of well-qualified black college students who were denied admission to their state law schools because of their race. His victories in those cases established the principle that racial discrimination in higher education violated the Constitution. The logic of that ruling then paved the way for a broad attack on segregation in all public schools throughout the South.
Similarly, Supreme Court Justice Ginsburg, an ACLU lawyer in the 1970s, sought to win equal rights for women by bringing seemingly narrow cases involving gender discrimination. She argued an equal-protection claim on behalf of Air Force Lt. Sharron Frontiero, who was denied medical benefits for her husband. At that time, the military said wives were entitled to benefits as dependents but husbands were not. The Supreme Court disagreed and said for the first time that such gender discrimination was constitutionally suspect.
In time, the justices said sex discrimination warranted a "heightened scrutiny" from courts. Under this standard, it could not be justified unless the government had a very strong reason. This rule did not mean that women had a right to serve in combat in the military, but nearly all other laws that discriminated based on sex were voided.
The Obama administration said last week that it believed this heightened-scrutiny standard was also the right way to judge discrimination based on sexual orientation.
That explains why gay rights advocates hailed the Obama announcement as a huge victory and one that is likely to echo far beyond the cases of legally married same-sex couples in New England. Bonauto said a Supreme Court ruling that says anti-gay discrimination is unconstitutional would have a far-reaching impact.
"If that legal standard takes hold, it would affect all anti-gay discrimination," she said.