Even as anti-abortionists celebrated that headline, some informed criticism of the Gallup findings has pretty clearly shown them to be an almost certain outlier, and highly misleading to boot.
First up, the partisan composition of the Gallup poll sample drew some attention--not surprisingly, since Gallup itself suggested that the "big shift" on abortion was occurring almost entirely among Republicans and Republican-leaning independents.
Charles Franklin at pollster.com made this discovery and observation:
The latest Gallup (5/7-10/09) poll has party identification tied at 32-32 and caused an immediate howl of "outlier!" in the comments at Pollster.com. In this case, the howl is justified. Compared to all recent Gallup polls (so we compare apples to apples) this latest stands out quite a bit from the rest.
Franklin also deals with the theory that polls which ask lots of questions on "values" issues tend to push the party ID numbers. In polling parlance, this is known as the "question order" effect. In the current case, a significant "question order" effect would imply that the abortion numbers are valid, while the party ID numbers may be emphemeral. But looking at similar Gallup surveys in the past, Franklin deduces that it's never been a factor before, and thus there's no reason to believe it's a factor now.
Thus Franklin concludes:
It is easier to be confident about the outlier status of this poll than to account for why it is so clearly out of line with previous Gallup results. At least we can address the outlier status empirically and with some statistical confidence. They "why" of that status must remain the always true maxim: "Outliers Happen."
So Gallup has published an outlier. But even if you disagree, what does the poll actually show, given the big broad strokes of "pro-choice" and "pro-life" opinions?
At the always-valuable academic site The Monkey Cage, John Sides takes a look at attitudes on abortion policy as indicated in the exceptionally long-range National Election Studies and General Social Survey. The former reinforces Nate Silver's post from last week emphasizing the stable pro-choice majority of abortion polling for a long, long time. And the latter underlines my own argument that all the top-line findings on abortion attitudes disguise high levels of support for exceptions to abortion restrictions that closely track the pro-choice position and the constitutional status quo.
In particular, GSS shows an exceptionally durable 80%-plus level of support for a "health exception," which happens to be the actual flash-point separating pro-life activists from the rest of the population. In other words, lots of "pro-life" Americans consistently, and over decades, favor an exception that pro-life activists adamantly consider a complete repudiation of the pro-life point of view.
So even if the Gallup folks are right (and they almost certainly aren't), that there's now a "pro-life" majority among Americans, it's meaningless in terms of support for a change in abortion policy. That may not get any headlines, but it's worth knowing.