Whatever the polls, the political crosscurrents are tricky, and administration officials conceded as much.
Some top aides argued that gay marriage is toxic at the ballot box in competitive states like North Carolina and said the vote there this week shows that opposition to the issue is a rallying point for Republicans.
Shifting his emphasis, even briefly, could open Obama up to Republican criticism that he is taking his eye off the economy, voters' No. 1 issue.
Yet some prominent gay donors have said publicly they wanted Obama to announce his support for gay marriage. Other Democratic supporters claim Obama's decision could energize huge swaths of the party, including young people. He also could appeal to independent voters.
By day's end Wednesday, the Obama campaign had emailed a clip of the interview and a personal statement from the president to its vast list of supporters, drawing attention to his stance.
The decision also creates an area of clear contrast between Obama and his Republican rival as he argues that he's delivered on the change he promised four years ago.
Obama said he sometimes talks with college Republicans on his visits to campuses, and while they oppose his policies on the economy and foreign policy, "when it comes to same sex equality, or, you know, sexual orientation, that they believe in equality. They are more comfortable with it."
Maggie Gallagher, co-founder of the National Organization for Marriage and a leading supporter of the constitutional amendment approved in North Carolina on Tuesday, said she welcomed Obama's announcement at the same time she disagreed with it.
"Politically, we welcome this," she said. "We think it's a huge mistake. President Obama is choosing the money over the voters the day after 61 percent of North Carolinians in a key swing state demonstrated they oppose gay marriage."
House Democratic leader Nancy Pelosi instantly sought political gain from the president's announcement. The Democratic Congressional Campaign Committee issued an email in her name that asked recipients to "stand with President Obama." Such requests are often followed by a solicitation for campaign donations.
Obama said first lady Michelle Obama also was involved in his decision and joins him in supporting gay marriage.
"In the end, the values that I care most deeply about and she cares most deeply about is how we treat other people," he said.
Acknowledging that his support for same-sex marriage may rankle religious conservatives, Obama said he thinks about his faith in part through the prism of the Golden Rule — treating others the way you would want to be treated.
"That's what we try to impart to our kids and that's what motivates me as president and I figure the most consistent I can be in being true to those precepts, the better I'll be as a dad and a husband and hopefully the better I'll be as president," Obama said.
Six states — all in the Northeast except Iowa — and the District of Columbia allow same-sex marriages. In addition, two other states have laws that are not yet in effect and may be subject to referendums.
AP Deputy Director of Polling Jennifer Agiesta and Jessica Gresko in Washington and Philip Elliott in Colorado contributed to this report.
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