Ten years ago, same-sex marriage was legal nowhere in the United States. It's now allowed in nine states, with several more in the pipeline, yet many other states seem unlikely to follow suit unless forced by Congress or the Supreme Court.
It seems like a recipe for long-term conflict, but President Barack Obama and other Democratic Party leaders are now firmly ensconced in the ranks of gay-marriage supporters, and national opinion polls suggest that's now the prevailing view among the public.
The campaign promise:
"It is important for me to go ahead and affirm that I think same-sex couples should be able to get married." — Obama in May 2012, ending his drawn-out "evolving" on gay marriage, which he had previously opposed.
Since his re-election, Obama's stance has become more emphatic, notably with a passage in his inaugural address placing the push for marriage equality in the same context as the civil rights crusades of blacks and women.
"Our journey is not complete until our gay brothers and sisters are treated like anyone else under the law, for if we are truly created equal, then surely the love we commit to one another must be equal as well," Obama said.
More recently, the Obama administration argued on behalf of same-sex marriage in two cases before the Supreme Court.
In one case, the administration argued that a section of the 1996 Defense of Marriage Act is unconstitutional because it denies legally married same-sex couples many federal benefits that are available to married heterosexual couples.
In the other case, Obama's team urged the Supreme Court to overturn California's voter-approved same-sex marriage ban and look skeptically at similar bans in other states. The argument fell short of an outright appeal for immediate legalization of gay marriage nationwide, but it was the first time a president had asked the high court to expand the right of gays and lesbians to wed.