I know when I think of cool and trying to relate to the youth, this automatically comes to mind...
In all seriousness, most politicians are going to be seen in this manner because they're adults. It's the same reason why when we grow up, we don't dress and talk like 19-year-olds. However, Bill Clinton is likable and charismatic. Obama is charismatic too although I detest that POS but his people were smart enough to pander to the celebrity obsessed culture and has been on so many talk shows and reality shows. That's why he referenced Jay Z songs, released his favorite shows he watches that just happened to be the ones everyone else likes and pushed his "cool hip black guy" image when the desired audience was around. It paid off.
Like I said, we live in a different time and not many presidents are going to be considered "cool" to college kids and that goes for both parties. And you're right about having to pander to the Christian crowd. They are handcuffed in that regard where as a Dem can have an "anything goes mentality." Want to pretend a guy that chops his dick off is now a woman and should use the same bathroom as your kid? Cool. No problem on the Dem side. No standards to disappoint.
I will say, you know Bush was probably pretty cool to hang out with and probably smoke a j with.