Ideally, science should inform many of the major policy decisions facing the US. As such, scientific questions are fair game for candidates for office. However, at last night's Republican Presidential candidate debate, scientific questions came up solely because people knew that this field of candidates would say something stupid in response. The field delivered.
The two areas touched on were vaccines and climate change. The former was motivated by Donald Trump's previous public pronouncements linking vaccinations to autism. The latter came up because members of the Republican party seem to have settled on a tactic of admitting they're not scientists and then suggesting that the actual scientists don't know what they're talking about.
The moderator, Jake Tapper, didn't pose the vaccine question to Trump. Instead, he asked Ben Carson, one of the MDs on stage, whether he'd be interested in correcting Trump on his claims regarding vaccines and autism. Carson came through, correctly noting that "there have been numerous studies, and they have not demonstrated that there is any correlation between vaccinations and autism."