With lots of specifics, John McCain has answered what Science Debate 2008 has determined to be "the 14 top science questions facing America." The questions, which cover a broad range of topics, including genetics, climate change, space exploration, and scientific integrity, were also sent to Barack Obama, who responded earlier this month.
On the topic of stem cell research, McCain says:

"While I support federal funding for embryonic stem cell research, I believe clear lines should be drawn that reflect a refusal to sacrifice moral values and ethical principles for the sake of scientific progress. Moreover, I believe that recent scientific breakthroughs raise the hope that one day this debate will be rendered academic. I also support funding for other research programs, including amniotic fluid and adult stem cell research which hold much scientific promise and do not involve the use of embryos. I oppose the intentional creation of human embryos for research purposes and I voted to ban the practice of “fetal farming,” making it a federal crime for researchers to use cells or fetal tissue from an embryo created for research purposes."

McCain also said that he believes policy should be based on sound science, he'll work quickly the fill the role of White House science adviser, and he'll make space exploration a "top priority" with an "agenda that will combine the discoveries of our unmanned probes with new technologies to take Americans to the Moon, Mars, and beyond."
The biggest question ScienceDebate2008 asks: Who will be the best president for America in a science-dominated world? Check out a side-by-side comparison of McCain's and Obama's answers and decide for yourself. —Heather Wax