Yes, Mitt Romney reaffirmed his opposition, and House Republicans messed around with the defense bill to make gay marriage an issue. But in their public comments, both Romney and House Speaker John Boehner were relatively restrained, as if they know that, politically, this is not in any way a slam dunk for the GOP.

Yes, much has changed since 2004, when the existence of referenda against gay marriage in swing states helped George W. Bush in his reelection campaign. As many have reported, the polls have moved steadily in gay marriage’s favor.

Moreover, Obama has followed the same trajectory as have so many Americans older than 45. They were concerned initially that changing the definition of marriage was too much to ask of their more traditionally minded fellow citizens but concluded that, if a society wishes to honor fidelity and commitment in relationships, it must extend equal-marriage rights to same-sex couples. My own views moved in exactly that direction, and I think that’s true of many older people, including many non-liberals.

Among Americans younger than 45, and especially those under 30, support for gay marriage is overwhelming. That’s why it is so hard to figure out the long-term political impact of Obama’s announcement, and why Republicans are being relatively cautious. Obama’s bold announcement will clearly revive some of the energy on his behalf among the under-30s that has been missing since the 2008 campaign.

And there may be a trade among the rest of the electorate. Economically moderate or conservative voters who are more socially liberal now have a reason to support Obama. (That’s what Romney has reason to worry about.) The president, in turn, may lose some votes among traditionally minded voters who are open to Democratic arguments about inequality. The bottom line, of course, is that most Americans won’t base their vote primarily on the gay-marriage issue.

One little-noted aspect of the president’s stand that will prove important: He is talking about provisions in the New York gay marriage law that protect the religious rights of traditions that oppose gay marriage. The government will not force gay marriage on more conservative churches, Orthodox synagogues or mosques. This is important because polls suggest that some of the opposition to gay marriage comes from those in more conservative traditions, who worry that government will interfere with their practices on marriage. The First Amendment already guarantees that this can’t happen, but legislating those protections is a way to make that clear. What we have here is a worthwhile democratic trade-off: we will honor the rights of gays and lesbians to get married on an equal footing but respect members of those congregations who still have qualms on religious grounds. Change within those traditions can (and I suspect, over the long run, will) come from within.

And despite the reports that Vice President Biden apologized for forcing the issue with his comments on “Meet the Press,” I think the president owes Biden a debt. The fact is that Obama had already signaled he had changed his mind on the issue when he announced his views were “evolving.” He couldn’t spend the whole campaign defending a process of evolution. He needed to take a stand eventually, and it was better to do so earlier than later.

I felt both elation and relief when I heard what Obama had done. As a general matter, it’s a good thing when a politician says what he or she actually thinks. And in this case, Obama set off a discussion in households and neighborhoods around the country that will advance the causes of understanding and justice.