Our take: Have presidential candidates responses to American's top science questions changed over the years? Shawn Lawrence Otto, co-founder of Sciencedebate.org, analyzes President Barack Obama's and Governor Mitt Romney's recent responses to questions on climate change and vaccines relating to autism.

"President Barack Obama and his challenger, Governor Mitt Romney, have answered 14 Top American Science Questions put to them by the grassroots nonprofit I lead, ScienceDebate.org. The candidates' answers provide valuable insight into their positions on issues that, while among the most important facing the country, usually get short shrift on the campaign trail. Here they are:/p>

"One of the most interesting highlights from the responses is Mitt Romney's shift on climate change, away from his most recent position, which was, 'My view is we don't know what's causing climate change on this planet,' back toward the view he held in June 2011, shortly after announcing his run for the presidency, when he acknowledged that people are significant contributors to climate change. Four days after he made that statement, Romney was slammed by Rush Limbaugh, who said, 'Bye-bye nomination. Another one down. We're in the midst here of discovering that this is all a hoax. The last year has established that the whole premise of man-made global warming is a hoax, and we still have presidential candidates who want to buy into it.'"