Participants at a rally in the Dallas neighborhood of Oak Lawn on May 9 applaud President Obama's stance on gay marriage. (Brad Loper/AP)

Public opinion continues to shift in favor of same-sex marriage, according to a new Washington Post-ABC News poll, which also finds initial signs that President Obama’s support for the idea may have changed a few minds.

Overall, 53 percent of Americans say gay marriage should be legal, hitting a high mark in support while showing a dramatic turnaround from just six years ago, when just 36 percent thought it should be legal. Thirty-nine percent, a new low, say gay marriage should be illegal.

The poll also finds that 59 percent of African Americans say they support same-sex marriage, up from an average of 41 percent in polls leading up to Obama’s announcement of his new position on the matter. Though statistically significant, it is a tentative result because of the relatively small sample of black voters in the poll.

The poll comes two weeks after Obama unexpectedly endorsed same-sex marriage after a year and a half of “evolving” on the subject. Gay rights groups predicted the president’s announcement would have a far-reaching impact on public opinion, in part because Obama described how he came to his own decision, referring to his gay friends and the influence of his young daughters, Sasha and Malia.

“By speaking in very personal terms about his own journey, the president has helped to build a larger and stronger majority in support of full equality for committed gay and lesbian couples,” said Fred Sainz, a spokesman for the Human Rights Campaign, a gay rights group that supports Obama’s reelection.

Seventy-one percent of Americans have a friend, family member or acquaintance who is gay, according to the Post-ABC survey, compared with 63 percent in 2010 and 59 percent in 1998.

The poll offers some insight into how same-sex marriage might affect voters’ decisions at the ballot box this fall. But the issue remains a significant wild card for the president as he seeks to overcome skepticism about his handling of the economy.

The president’s announcement may prove to be a wash: Most Americans say Obama’s stance on gay marriage will not play a big role in their vote for president. And the number of voters who say it makes them more apt to support Obama’s bid for reelection is roughly the same as the number who say they are now more likely to oppose a second term for him.

Frank Schubert, national political director for the National Organization for Marriage, a prominent group opposed to same-sex marriage, called into question the accuracy of the poll, noting that polls frequently have overestimated support for same-sex unions in advance of votes on state ballot measures.

In all 30 states where voters have been asked to approve or reject same-sex marriage, they have rejected it. In places where it is legal — six states and the District — it was made so by an act of the state legislature or the courts.

Americans divide about evenly — 49 to 46 percent — on whether gay-marriage laws should be made at the state or federal level. Most backers of same-sex marriage support a federal approach, while opponents prefer letting states decide. That is a stark shift from 2004, when a CBS News-New York Times poll found widespread support for federal authority over gay marriage among its opponents, not its supporters.

Schubert was deeply skeptical that support for same-sex marriage was increasing among African Americans.

“There is not a chance in God’s green earth that African Americans support same-sex marriage,” he said, drawing from his experience organizing anti-same-sex marriage campaigns in California, Iowa, Maine and North Carolina. The president’s endorsement has likely “created a lot of angst and conflict in that community, but his opinion of same-sex marriage is not going to be changing the opinion of African Americans in a significant way.”

Polling director Jon Cohen and polling manager Peyton M. Craighill contributed to this report.