I think Rubio is a nice guy, but to me it seems like he lacks the leadership personality one needs to be a president. His posture reminds me of Cory Booker. Both of them are smart, personable, and relatively articulate, but to me they both seem to always be looking over their shoulder to see if everyone is following behind them. A good leader has to have a stronger backbone and a more healthy level of self-confidence.
Ego is not the same as confidence.