He's hot. That's about the only thing he has going for him.
Obama would still win in terms of the "cool" factor especially among younger voters since John Thune is such a social conservative, which would mean Obama would still hold and probably strengthen his hold on younger voters because of the social issues.
I don't think young people vote exclusively on social issues. Why would they?
Because by and large they're incredibly stupid. Most younger people only really care about image. There are a few smart ones out there, but frankly I think most people need to get into their 30's before finding out what they actually believe, if they ever do.