Obama accepted the challenge, and answered all the questions at length, while John McCain declined (although Nature have pieced together answers based on what he's said in the past). The answers are in two parts - Part one includes evolution, stem cell research and others, and Part two features, among other things, emissions targets, coal-fired power stations and nukes.
It's lengthy stuff, so I'll leave you to read them yourselves, but to give you a preview here are the answers to the question: "Do you believe that evolution by means of natural selection is a sufficient explanation for the variety and complexity of life on Earth? Should intelligent design, or some derivative thereof, be taught in science class in public schools?"
Obama: I believe in evolution, and I support the strong consensus of the scientific community that evolution is scientifically validated. I do not believe it is helpful to our students to cloud discussions of science with non-scientific theories like intelligent design that are not subject to experimental scrutiny.Hmmm - we'd love to hear Sarah Palin's answer to that one.
McCain: He said last year, in a Republican primary debate: "I believe in evolution. But I also believe, when I hike the Grand Canyon and see it at sunset, that the hand of God is there also." In 2005, he told the Arizona Daily Star that he thought "all points of view" should be available to students studying the origins of humanity. But the next year a Colorado paper reported him saying that such viewpoints should not be taught in science class.