A plan to hold a presidential debate on science and technology issues in Philadelphia, Pennsylvania, next week has failed. Now organizers hope to stage the event on 9 May in Oregon. But with candidates careful to avoid missteps, that plan faces tough odds. Launched in December, ScienceDebate2008 is a grass-roots movement to hold a national discussion on science and technology issues, including stem cell research, climate change, and science education. Dozens of the nation's science organizations are behind it, including the American Chemical Society, the American Society of Plant Biologists, and the American Association for the Advancement of Science (AAAS),...