I've seen quite a few claims that Bill Frist has abandoned his pro-life principles by proposing federal funding for using stem cells from embryos that will be discarded anyway. See IntolerantElle's post and the links from there for examples. This post started as a comment on her post.
I think this argument goes too far. Frist isn't necessarily inconsistent on this. It's not clear at all that he's contradicting his pro-life stance. What he's proposing is that it's no more wrong for someone to kill these embryos by extracting stem cells than it is simply to throw them away. They will be destroyed. There's no way to prevent that given the current law that these embryos are the property of parents. He's suggesting that in destroying them the stem cells should be retained so that at least this immoral action can have some good consequences.
Nazi war crime experiments are a good analogy. The experiments were clearly wrong. What was also wrong was when the idiot Allied leaders insisted on throwing out the results of that research, as if the mere existence of the knowledge gained by immoral means has some immoral element. If we learned that we can cure cancer via a moral method, and the way we learned it was by finding the research of a scientist who did terrible things to people to find this information, we have a moral responsibility to preserve that knowledge, not to throw it out. You might even think it would be dishonoring to those who suffered at the hands of these scientists if you threw out the good that came of it.
Similarly, with stem cells, it may be immoral for these parents to kill their embryonic children, but the law gives them the right to do it. All Frist is proposing is that we extract the stem cells before we do it. Maybe there are moral considerations against that (e.g., having to do with honoring corpses unless they consent to have their bodies used for medical research), but it can't be merely because of the pro-life issue, because these embryos are going to be destroyed either way. Wanting to prevent that from being as much of a tragedy by using their stem cells to help people is not a clear contradiction with the pro-life view.
Frist would admit that the discarding of these embryos is a tragedy, but I think what he's going to insist on is that throwing out the stem cells with the embryos is even more immoral, and since we can't legally stop the throwing out of the embryos (with much more court precedent than would make it easy to pass a law to stop) we can at least save the stem cells and see if some good can come of it (which a law can much more easily allow). Add to this that what Frist wants to fund is already legal in itself but just isn't legal to use federal funding for. The laws on stem cell harvesting and embryo destruction are pretty loose compared to the laws on federal funding for such actions. Frist is proposing the the government step in to prevent a tragedy from being even worse of a tragedy. That does not in any clear or necessary way amount to a contradiction with pro-life principles.
You can put together an argument in defense of the Bush position against Frist's view, but I don't think it's going to involve premises that every pro-life person would share, and apparently Frist doesn't share the premises of the Bush argument. I'm not sure if I do. I'd have to see a more careful version of the argument than what people keep saying. All they say is that he's abandoned his concern that embryos are human beings with moral rights, which he hasn't done at all. He's simply said that taking something from someone whose rights are being violated, in a way that you can't stop, may actually be morally imperative rather than morally wrong.