There are two previously unreported problems with the stem cell lines approved by the Bush administration, the Washington Post reports today. One study finds that all approved lines share a previously unrecognized trait that fosters rejection by the immune systems, “diminishing their potential as medical treatments.” And another study has concluded that at least one-fourth of the approved lines (there are 22 of them) are so difficult to keep alive that they have little potential, even as research tools.

Such news may be too late to affect the presidential election–and no doubt anyone who’s going to vote on the single issue of stem cells has already made up his or her mind one way or the other–but it might add yet more wood on the fire of California’s Proposition 71. In a recent poll, 53% of respondents favored Prop. 71’s passage and only 34% opposed.