Bill Frist’s decision to back an expansion of stem cell research is fascinating. Frist has been assiduously courting Christian conservatives for years in anticipation of a presidential run. So why did he decide to burn them now on a litmus test-type issue?

Some possibilities:

1) He decided that stem cell research is just too popular to resist. The fact that someone like Frist would back stem cells suggests that this issue is a political loser for conservatives and will soon be conceded by everyone to the left of Rick Santorum.
2) He realized that he’s not the candidate of choice for conservatives, so he’s trying to appeal to a broader swath of the Republican primary electorate and build up his general election appeal.
3) He realized that backing stem cell research plays up his greatest personal strength — his medical background.
4) After months of shameless pandering, he went with his instincts as a doctor rather than making a political calculation.

The stem cell debate is, of course, closely related to the abortion debate, but with one key difference — it’s playing out in the political realm without court involvement. So it’s a great test of the hypothesis that abortion politics are so polarized because Roe v. Wade removed the issue from the democratic process and prevented compromise. If that hypothesis is correct, then conservatives should eventually accept the legitimacy of stem cell research. The fact that so many conservatives have already accepted President Bush’s original plan — which allows for the destruction of embryos — suggests that the Roe theory is correct. Frist’s decision may be another step down that road.