Pollsters have used this tactic for years. I admit I don't know if that Gallop poll did. But, your constant trumpeting of the middle group who are basically "pro-life" but support abortion in some cases leaves the poll open to such criticism. Plus, your attempt to approbate the entire group in that middle ground to the "pro-choice" side is dubious. Only 26% of those polled believe in abortion for any reason at any time. It would be just as easy to say the pro-choicers are in the minority.
BTW, I just finished the first volume of Ian Kershaw's masterful biography of Adolf Hitler. As the final chapter came to a close, Hitler had just militarized the Rhineland and called for new elections. The people voted for him and his party at a rate of 98.6%. I guess they were right, too.
The value in polls is not to determine who is right or who is wrong. The real value lies in feedback. Am I making positive or negative progress. For example, the latest Gallop Poll on abortion shows that:
Something happened around 1998. Before that time there were more Pro-Lifeers than there were Pro-Choicers. After that point, the Pro-Choicers began to outnumber the Pro_Lifers. The Pro-Choicers continue to out number the Pro-Lifers with a growing margin.
It would seem that something happened that caused this shift. Would you like to know what is was?