At the GOP debate in Sioux City, Iowa, Newt Gingrich defended his pro-life record, declaring, “I believe that life begins at conception” and stating that embryos at fertility clinics “should be considered life because by definition they’ve been conceived. I am against any kind of experimentation on embryos. And I think my position on life has been very clear and very consistent.”

No, it hasn’t. In an interview just two weeks ago, Gingrich said precisely the opposite. ABC News’s Jake Tapper asked Gingrich about his comments that “these fertilized eggs, these embryos are not yet ‘pre-human’ because they have not been implanted. This has upset conservatives in [Iowa] who worry you don’t see these fertilized eggs as human life. When do you think human life begins?” Gingrich replied: “Well, I think the question of being implanted is a very big question. … I think that if you take a position when a woman has fertilized egg and that’s been successfully implanted that now you’re dealing with life, because otherwise you’re going to open up an extraordinary range of very difficult questions.” Tapper followed up “So implantation is the moment for you?” Gingrich replied: “Implantation and successful implantation.” In other words, Gingrich’s position is not that life begins at conception, or even implantation, but at successful implantation.

This was not the first time Gingrich made such a claim. As National Review’s Ramesh Ponnuru has pointed out, as President George W. Bush was grappling with the stem cell issue in 2001, Gingrich launched a media campaign to allow such medical experimentation on human embryos. In an interview on Fox News, Gingrich urged Bush to support “research on cells that are in fertility clinics that have never been in anyone’s body, in terms of being — becoming a person,” adding “for many of us, there’s a very, very real distinction between doing something with an unborn child, a fetus that is implanted, and doing something with cells in a fertility clinic that are otherwise going to be destroyed.” A few days later, on “The O’Reilly Factor,” he again asked Bush “to look at fertility clinics where there are cells that are sitting there that are not going to be used to create life.. . . I hope the president will find a way to agree that there ought to be federally funded research.” When asked by ABC News’s Sam Donaldson, “So he [President Bush] should approve stem cell research on embryos?,” Gingrich replied, “On embryonic cells that — that are pre-fetal.” If life begins at conception, as Gingrich now claims to believe, there are no embryonic cells that are “pre-fetal.” He was advocating medical experimentation on what he now acknowledges is human life. Fortunately, Bush rejected Gingrich’s advice.

Gingrich’s abortion contortions should be a major vulnerability for him in Iowa. While Republicans in the Hawkeye State are focused on the economy like the rest of America, protecting human life is a sacred issue for many of them. The question is: Why hasn’t Romney done more to exploit Gingrich’s flip-flops on this issue? When Gingrich made his comments to ABC News this month, Romney was silent. And during the Sioux City debate, Romney passed on the opportunity to point out that while Gingrich said just weeks ago that he believes life begins at implantation, as Massachusetts governor he vetoed legislation that would have changed state law to define life as beginning at implantation. And while Gingrich and other candidates spoke last week in Des Moines at a screening of Mike Huckabee’s new film, “The Gift of Life,” (which recounts stories of children who survived abortion, including those adopted as frozen embryos), Romney was the only major candidate save Ron Paul not to show up.

For all the conservative angst over the genuineness of Romney’s conversion on life, at least he changed his position on embryonic stem cell research six years ago — not two weeks ago as Gingrich did. When the issue was before him and his decision mattered, Romney made the right choice. Gingrich, by contrast, publicly urged Bush to make the wrong choice. Not only has Romney promised to overturn Obama’s stem cell policy, he has a robust pro-life agenda planned for his administration. A top Romney adviser told me that, as president,Romney would support a raft of pro-life legislation — from pain capable unborn child protection legislation (like that recently passed in Nebraska) to the Child Interstate Abortion Notification Act. Considering Gingrich’s troubling statements and legislative history, Romney can credibly argue that in a race with Gingrich, he is the more pro-life candidate.

With the Iowa caucuses just weeks away, why isn’t he making that case?