Has he said he won’t support him?
No? Then what’s the question?
Rubio’s decision to call Trump a “Con Artist” means Rubio cannot support Trump in the Fall Campaign. You can’t call a fellow-candidate a “Con Artist” and intend to support that person against the Democrats. Rubio is going scorched earth, because he believes this will either gain the nomination for himself, or pave the way for Trump’s defeat in the Fall - meaning he can run again in 2020.