The platform approved at the Democratic convention in Charlotte included a plank supporting same-sex marriage. Last week, Obama urged voters to back initiatives in Maryland, Maine and Washington state to allow gay couples to marry; he had previously urged Minnesotans to vote against a marriage prohibition.

If this is exacting a political price, it’s hard to discern. Republicans and their nominee, Mitt Romney, have not raised the subject — not at their convention, not on the campaign trail, not during the debates. …

The difference is striking. I remember questioning a parade of Democratic presidential contenders about same-sex marriage during the 2004 campaign. They would stammer and talk about hospital visits, maybe civil unions. Their aides would glare at me for broaching this unwelcome topic. …

In 2004, 16 percent of Republicans backed same-sex marriage; by 2011, 26 percent did. In 2004, 33 percent of self-described moderates supported marriage equality, by 2011, 54 percent were in favor. And although the Catholic Church is a major financial backer of groups opposing same-sex marriage, support among Catholics has grown from 35 percent to 52 percent.

From ultimate wedge issue to relative nonissue — a stunning transformation.