Why not? The reason has to do with the nature of wedge issues, which are rarely about the narrow debate that brings them into public view (such as stem-cell research in this case). Instead, they tend to be proxies for much deeper-seated emotions or anxieties, which the wedge issue inflames. For an issue to work as a wedge, it's the emotional subtext that has to cut your way.Scheiber illustrates how Republicans often benefit from this, and Democrats less so -- because of the way the underlying emotional issues play.
For example, how is it that Bush used the Iraq war to his advantage in 2004 even though more than half the country had serious reservations about it? The answer is that the debate wasn't about the Iraq war per se. It was about Bush's toughness and resolve on the one hand, and Kerry's weakness and indecisiveness on the other. By running on the war's metaphorical meaning rather than the war itself, Bush managed to unite his own side and split Democrats--a textbook wedge maneuver. (According to exit polls in 2004, 53 percent of voters viewed Bush favorably, about the same number that thought the war was going badly and had made the United States less safe.)Check it out. It's a good article to read before we hypnotize ourselves into thinking that because we're aligned with a good cause -- one the public agrees with -- the voters will all necessarily vote our way on this.
I suspect there's a similar dynamic at work when it comes to stem-cell research. Here the substantive merits pretty clearly point in one direction (it's a good idea), but the metaphorical value to Democrats may be limited at best. That's because underlying the stem-cell issue is a deeper debate about the way science is changing our lives. On one side of this debate are those who believe biotechnology is mostly a force for good, and that reining it in is basically reactionary. On the other side are those more troubled by the moral and ethical questions raised by advances in biotechnology. The problem for Democrats is that the American public splits a lot more evenly on these questions than it does on the narrower question of whether to extract stem cells from discarded embryos.
Politics is not that rational, for better or worse.