WASHINGTON (CNS) -- Less than four months into President Barack Obama's term, opinion polls are finding that Americans are taking a dramatic turn toward greater opposition to abortion.

A poll conducted May 7-10 as part of the annual Gallup Values and Beliefs survey found that a majority of Americans (51 percent) described themselves as "pro-life" with respect to the abortion issue, while only 42 percent said they were "pro-choice." The results were made public May 15.

It marked the first time since Gallup began asking the question in 1995 that more respondents said they were pro-life than pro-choice, and was a shift of 7-8 percentage points from a year earlier, when 50 percent said they were pro-choice and 44 percent said they were pro-life.

Obama is a strong supporter of keeping abortion legal. Some groups that promote abortion have said his November 2008 election was a mandate to expand access to and federal funding of abortion.

A separate Gallup Poll Daily survey conducted May 12-13 found that 50 percent of Americans described themselves as pro-life and 43 percent as pro-choice.

The results were similar to another national survey made public April 30 by the Pew Research Center for the People & the Press, which found that the number of Americans who said abortion should be legal in all or most cases had declined to 46 percent in April 2009 from 54 percent in August 2008.

Forty-four percent of respondents in the Pew poll said abortion should be illegal in most (28 percent) or all cases (16 percent), up from 41 percent in August 2008.

The margin of error for each of the three polls was plus or minus 3 percentage points.

The Gallup Values and Beliefs survey found the strongest pro-life views among those who said they were Republican or independents leaning toward the Republican Party, those who described themselves as conservative and those who said they were Christians.

Fifty-two percent of the Catholic respondents and 59 percent of Protestants or members of other Christian religions described themselves as pro-life in the 2009 poll, compared to 45 percent of Catholics and 51 percent of Protestants in May 2008.

Seventy percent of Republicans or those leaning Republican said they were pro-life, compared to 60 percent in 2008; the percentage who said they were pro-choice in that group dropped from 36 percent in 2008 to 26 percent this year.

Among Democrats and independents who leaned toward the Democratic Party, the position on abortion remained virtually unchanged, with 61 percent saying they were pro-choice and 33 percent pro-life in 2009, compared to 60 percent pro-choice and 33 percent pro-life last year.

"With the first pro-choice president in eight years already making changes to the nation's policies on funding abortion overseas, expressing his support for the Freedom of Choice Act and moving toward rescinding federal job protections for medical workers who refuse to participate in abortion procedures, Americans -- and, in particular, Republicans -- seem to be taking a step back from the pro-choice position," said a Gallup commentary on the results.

"It is possible that, through his abortion policies, Obama has pushed the public's understanding of what it means to be 'pro-choice' slightly to the left, politically," it added. "While Democrats may support that, as they generally support everything Obama is doing as president, it may be driving others in the opposite direction."

When Gallup first began conducting the Values and Beliefs survey in 1995, 56 percent of Americans described themselves as pro-choice and only 33 percent said they were pro-life. Since then, the highest percentage to identify themselves as pro-life was 46 percent, in both August 2001 and May 2002.

In surveys conducted by Pew Research, support for keeping abortion legal in all or most cases ranged in 2008 from 57 percent in mid-October to 53 percent in late October but dropped to 46 percent in April 2009.

Copyright © 2009 Catholic News Service/U.S. Conference of Catholic Bishops