New York ? A Gallup Poll released Friday found that 51 percent of Americans now call themselves pro-life rather than pro-choice on the issue of abortion, the first time a majority gave that answer in the 15 years that Gallup has asked the question.

The findings, obtained in an annual survey on values and beliefs conducted May 7-10, marked a significant shift from a year ago. A year ago, 50 percent said they were pro-choice and 44 percent pro-life — in the new poll, 42 percent said they were pro-choice.

The new survey showed that Americans remained deeply divided on the legality of abortion — with 23 percent saying it should be illegal in all circumstances, 22 percent saying it should be legal under any circumstances, and 53 percent saying it should be legal only under certain circumstances.

The findings echoed a recent national survey by the Pew Research Center, which reported a sharp decline since last August in those saying abortion should be legal in all or most cases — from 54 percent to 46 percent.

Taken together, the two polls have elated anti-abortion activists, who had been stung by the November election results that placed President Barack Obama and other abortion-rights supporters in power in Washington.

“Ironically, Obama’s radical abortion policies and nominees may have helped make America more pro-life,” said Wendy Wright, president of the conservative advocacy group Concerned Women for America.

The Rev. Richard Land, president of the Southern Baptist Convention’s Ethics & Religious Liberty Commission, said the poll findings demonstrate that the anti-abortion cause “is a vibrant, growing, youthful movement.”

“We are winning the battle for hearts and minds in our culture on the life issue,” he said.

The president of a leading abortion-rights group, Nancy Keenan of NARAL Pro-Choice America, said the Gallup findings “do not square with the voting patterns in the last two elections cycles.”

“It would be a mistake for anti-choice groups to interpret this one poll as a signal that Americans want even more interference from politicians in their personal, private decisions, including a woman’s right to choose safe, legal abortion,” Keenan said.

Another abortion-rights leader, Planned Parenthood Federation of America president Cecile Richards, questioned the terminology in the Gallup questions.

“The terms pro-choice and pro-life no longer define the parameters of the debate, witnessed by the fact that in the Gallup Poll, a majority of people say they are both pro-life and that abortion should be legal,” Richards said.

She added that most Americans share Obama’s stated goal of reducing the number of unintended pregnancies.