Obama Credit: Getty Images

President Barack Obama's political calculus is clear.

His newly stated support for same-sex marriage could energize some Democratic Party activists. And it may illustrate a wider strategic effort to keep Mitt Romney from grabbing the perceived political center as he emerges from the Republican primaries.

That center shifts -- sometimes so dramatically that a formerly fringe idea grows acceptable enough within one generation for a major-party president to give it his symbolic backing.

At the same time, same-sex nuptials will remain a matter to be decided by states. So on this issue, Obama can just proclaim his view and have an instant impact without having to bargain with Congress as he would if it involved federal legislation.

Next week Obama rolls into New York again, to address Barnard College graduates and attend fundraisers by those sympathetic to the cause. Nassau Conservative Party chairman Daniel F. Donovan Jr., who consistently with his party opposes same-sex rites, described the politics plainly the other day when he told Newsday: "He wants to get re-elected, so he's going to his base."

That especially goes for New York, a state rendered "deep blue" largely by New York City. Some analysts, however, say Obama takes a risk in swing states. One longtime Democratic gay activist in Manhattan politics, who declined to be identified because he has a government job, said: "I imagine there are risks in those battleground states." But, he added, "those voters might not have voted for him anyway."

"This makes him sound statesmanlike," the activist said. "He's been really reaching out to a lot of the constituent groups that helped get him elected in '08 -- young people on tuition, Hispanics on immigration issues, women generally on health care and abortion, the gay community. And, African-Americans will still vote for him even if there's disagreement on gay marriage."

Others saw the rollout of Obama's position as clumsy and less effective than it could have been.

The accepted narrative out of Washington, D.C., goes that by backing gay marriage first, Vice President Joe Biden forced Obama to complete his "evolution" on the issue sooner rather than later. In the midst of the 2008 campaign, he declared, "I believe that marriage is the union between a man and a woman. For me as a Christian it is also a sacred union." Obama sounded at the time just like Romney did this week when Romney said: "My view is that marriage itself is between a man and a woman."

A New York Democratic strategist said under condition of anonymity: "If this was really being plotted for a while, Obama should have done it during the Republican primaries when it could have inflamed things and gotten the right to beat up more on Romney. . . . In Day 5 of the campaign, you have a major flip-flop. How does Obama now hit Romney for flip-flopping on abortion?"

Timing aside, Obama made an effort in his televised interview with Robin Roberts on ABC to square the position with his religious posture.

Obama noted he and his wife, Michelle, are both practicing Christians. "And obviously," he said, "this position may be considered to put us at odds with the views of . . . others. But you know, when we think about our faith, the thing . . . at root that we think about is not only Christ sacrificing himself on our behalf, but it's also the golden rule, you know? Treat others the way you'd want to be treated."

Evolution, calculus, religion, and verbal gymnastics are all required subjects in the curriculum of major-party politics.