Trying to be totally objective, not political... and I mean it with the Presidents or Presidential Candidates in the past 20 or 30 years ...
Reagan - Coherent. Good until right near the end when hints of the Alzheimers started setting it.
Bush Sr. - Coherent
Clinton - Coherent
Bush Jr. (W) - Spoke after he tried to think but often sadly made no sense
Obama - Coherent
Trump - Talks before he thinks - wait 24 hours until he does a 180 after he thinks
Biden - Speaks while he's trying to think but sadly often makes no sense