Romney is sane by comparison, but he caved to the right wing, religious base of the party, ridiculousness. The insanity about him running is I can’t imagine most people take it seriously when he has run for President so many times. Although, maybe the people who loved him are very happy he is running again.
Rubio is, ugh, a nightmare in my opinion. I think many democrats feel about Rubio the way many republicans felt about Obama. Not enough experience, and wants to change too many things democrats disagree with, and very possible a party puppet.
I think Bush is sane, and should be taken as a serious candidate. The biggest problem he has is the legacy of his brother. Most Republicans won’t mind the legacy, I think independents and democrats will. This whole confederate flag thing in the news I think helped Jeb Bush just a little with the independents, but it’s too early to be able to tell anything.