I think he is an idiot on climate change, but I consider Rubio an electable conservative. I am not even a conservative by any measurement, but I can see him becoming President one day.
I actually think Rubio has a decent shot to be a US President but not in this election. Further down the line. He is still young for this post at 44. If he had won this Presidential Election, he would be the youngest President since JFK. The GOP Party Hierarchy didn't want him to run this time because they supported the more experienced Jeb Bush in this cycle. They must be melting down that an outsider in Trump is hijacking their party and the biggest establishment contender in Cruz is someone they hate.
Rubio will be more influential within the GOP Hierarchy in a decade from now. The GOP will need the Latin vote if they want to win a Presidential election again, and Rubio could help them with that. It is not really helping this cycle because led by Trump, the GOP nominee candidates are taking a hardline on illegal immigration, and bashing Mexico. Imagine him running with the financial backing that Jeb Bush got, more experience of debates and public speaking, and without a wild card like Trump hogging the media cycle.
I think the GOP will need to change to win a Presidential election again, but once they acknowledge this, and implement changes, then Rubio could be a leading contender again.
He's also ahead in Detroit, but it's way too early to tell though.