People celebrating the defeat of the marriage amendment energized the crowd gathered for a "United for Our Future" post-election rally Wednesday, Nov. 7, 2012 on the Capitol mall in St. Paul. MPR Photo/Jennifer Simonson

By JENNIFER C. KERR

Associated Press

WASHINGTON (AP) — The nation's views on gay marriage are more favorable in large part because of a shift in attitudes among those who know someone who is gay or became more accepting as they got older of gays and lesbians, according to a national survey.

The Pew Research Center poll also finds that a large group of younger adults who tend to be more open to gay rights is driving the numbers upward. The issue has grabbed the national spotlight recently with the public embrace of same-sex marriage by Democrat Hillary Rodham Clinton and Republican Sen. Rob Portman of Ohio.

"We've certainly seen the trend over the last ten years," Michael Dimock, director of the center, said Wednesday. "But we're now really in a position to talk about the combination of generational change and personal change that have sort of brought the country to where it is today."

Overall, the poll finds 49 percent of Americans favor allowing gays and lesbians to marry legally, and 44 percent opposed to the idea. That's more people now favoring same-sex marriage than opposing it. A decade ago 58 percent opposed it and a third supported it.

The 49 percent who now support same-sex marriage includes 14 percent who said they have changed their minds.

When asked why, almost one-third say it's because they know someone who is gay — a family member, friend or acquaintance. A quarter said their personal views have changed as they thought more about the issue or just because they've grown older and more accepting.

"...We're now really in a position to talk about the combination of generational change and personal change that have sort of brought the country to where it is today."

One of those polled said: "My best friend from high school is a gay man, and he deserves the same rights," adding that his friend and a partner "are in a committed relationship."

Another person attributed the shift in attitude to "old fashioned ignorance," and said "I grew up a little bit."

Just 2 percent overall said their views have shifted against same-sex marriage.

Another major factor in the long-term shift in the public's view: the so-called millennial generation of young adults born since 1980— today's 18- to 32-year-olds who entered adulthood in the new millennium. The survey finds 70 percent of millennials favor same-sex marriage.

Gay marriage has long been an issue of partisan political debate, but it resurfaced recently with Clinton and Portman declaring their support, and as the Supreme Court prepares to take up the issue.

On Monday, Clinton announced her support for same-sex marriage — lining up with other potential Democratic presidential candidates who favor it.

In an online video released by the gay rights advocacy group Human Rights Campaign, Clinton says that gays and lesbians are "full and equal citizens and deserve the rights of citizenship."

And last week, Portman reversed course and said he now supports same-sex marriage. He said he had a change of heart after he learned one of his sons is gay. "I have come to believe that if two people are prepared to make a lifetime commitment to love and care for each other in good times and in bad, the government shouldn't deny them the opportunity to get married," he wrote in an op-ed in The Columbus Dispatch. His reversal makes him the only Republican in the Senate to back same-sex marriage.

The Supreme Court will hear arguments next week in a challenge to a provision of the Defense of Marriage Act — the federal law that defines marriage as between one man and one woman. It's also reviewing California's Proposition 8 ban on same-sex marriage.

The Pew Research findings are based on a survey of 1,501 adults nationwide conducted Mar. 13-Mar. 17. The poll has a margin of error of plus or minus 3 percentage points.

Associated Press Director of Polling Jennifer Agiesta and News Survey Specialist Dennis Junius contributed to this report.