Gallup has polled on abortion for decades, ever since Roe v Wade overturned state bans on the procedure.  Two years ago, Gallup f0und that the pro-life position had taken a majority for the first time (51/42), but retreated somewhat in 2010 to a narrow 47/45 plurality.  Their latest poll, released today, gives the pro-choice position a plurality edge for the first time in three years:

Americans are closely divided between those calling themselves “pro-choice” and those who are “pro-life,” now 49% and 45%, respectively, in Gallup’s 2011 update on U.S. abortion attitudes. This is similar to a year ago, when 45% were “pro-choice” and 47% “pro-life.” However, it is the first time since 2008 that the “pro-choice” position has had the numerical advantage on this Gallup trend.

However, a majority still believes abortion to be morally wrong:

Gallup’s 2011 Values and Beliefs survey, conducted May 5-8, finds a bit more public agreement about the morality of abortion. Just over half of Americans, 51%, believe abortion is “morally wrong,” while 39% say it is “morally acceptable.” Americans’ views on this have been fairly steady since 2002, except for 2006, when they were evenly divided.

That has been true for almost the entire polling series.  Only in three years over the past ten has a majority failed to support the morally-wrong position (2001, 2006, and 2008).  Despite that, in most years since the 1975 start of the polling series, a majority supports legalized abortion “under certain circumstances.”  The position of legal under all circumstances has never had more than 34% support in almost four decades of polling, and it around the historical average this year at 27%.  Those supporting the position of making abortion illegal under all circumstances hit its historical high in this poll, but that’s only 22%.

The American populace seems to still be in flux on this question, but LifeNews puts a positive spin on it:

By a 24 percent margin, 61-37 percent, Americans take the pro-life view that abortions should either be legal under no circumstances or legal only under a few circumstances. Although Gallup doesn’t specify those “few” circumstances, polling data has consistently shown that, when asked about cases such as rape,  incest, or the life of the mother, a majority of Americans want all or almost all abortions made illegal — leaving only life of the mother or rape and incest as the exceptions.

“Americans are rather conservative in their stance on abortion, with 61% now preferring that abortion be legal in only a few circumstances or no circumstances. By contrast, 37% want abortion legal in all or most circumstances,” Gallup analyst Lydia Saad writes. “Over the past two decades, Americans have consistently leaned toward believing abortion should be legal in only a few or no circumstances, although less so in the mid-1990s than since about 1997, when combined support for these has averaged close to 60%.”

In fact, Gallup polling shows that, since 1994, a majority of Americans have held a pro-life view wanting all or almost all abortions made illegal — and that pro-life view has strengthened with an average of 60 percent of Americans saying that over the years.

The changes this year look like they could be classified as statistical noise.  However, after the 2009 result, the pro-life movement thought they had started to build momentum.  This poll suggests that more hard work is ahead before that becomes the case.

Update: My friend Steve Ertelt from Life News responds:

I believe the momentum has indeed shifted towards the pro-life side – though it’s actually more accurate to say that the momentum has always been on the pro-life side. Both the Gallup poll and polling data from other sources have shown for the last 20 years that most Americans oppose most abortions. Nothing’s really changed in that regard despite minor hiccups one way or the other in the numbers.
Looking at the current Gallup poll, its not correct to say the momentum has shifted against the pro-life side, if anything, the momentum has grown. The self-description of pro-life versus pro-choice is a misnomer as the terms have become confused and misleading to many people. Anecdotally, I had a good friend at church recently tell me she has always thought of herself as pro-choice. When asked to give details about her position on abortion, it’s clear she completely and totally opposes it. She’s clearly pro-life and doesn’t realize that’s the case and the Gallup poll makes that apparently, especially for the 10 percent of people 18-34 (including my friend) who can’t say whether they are pro-life or pro-choice on abortion despite the issues remaining the same their entire life.

The Gallup poll itself makes it clear that, on the morally wrong and legal/illegal questions, Americans have held remarkably stable views opposing all or most abortions. In fact, comparing the current poll to the previous poll shows the number of Americans who want all or most abortions illegal has increased 5 percent, and the number wanting all or most legal has dropped 2 percent even as the pro-life/pro-choice numbers flip-flopped. That’s a 7 percent pro-life shift from 2009-2010 in actual abortion views in terms of legality versus apparent abortion views based on PR/debate language (pro-life vs. pro-choice).

The actual versus perceived momentum is the key here also in terms of what is happening in the real world.
The drive to de-fund Planned Parenthood is one result of the real-world shift in momentum on the pro-life side. In years’ past, the pro-life side lost the vote by wide margins – if a vote was even taken because the expectation of a landslide defeat. The House has its biggest pro-life majority following the 2010 elections and, for the first time since Roe, the House approved cutting off taxpayer funding for Planned Parenthood. A change of hands in the Senate and White House next year could easily make that bill law. States are also passing record numbers of pro-life bills on all sorts of issues and by lopsided majorities in some cases.

The extensive exposes’ of Planned Parenthood by Live Action, the horror stories like Kermit Gosnell’s, and the buildup in opposition to Planned Parenthood like never seen before is a manifestation of the shift in pro-life opinion. And with Americans favoring the prohibition of abortion by a massive 61-37 percentage point margin, it’s no wonder there’s so much movement. And it sets up 2012 as a battle for the heart and soul of the Supreme Court that is very likely one vote away from overturning Roe and beginning the movement to legally protect women and unborn children from abortion.