For the life of me, I can't even comprehend how absolutely delusional Rubio must be in order to give up his prominent Senate seat in order to make a quixotic charge at the Republican nomination that we all know he has no chance of winning.
I don't think he has *no* chance of winning the nomination. He has a much better chance than the majority of the candidates who are/will be running.
In any case, as I think I've said before, Rubio doesn't care about his Senate seat. It's just a stepping stone to the White House for him. And even if he doesn't win the nomination this time, if he manages to make a strong showing of it, it could set him up for another run in 2020. Alternatively, if Walker, or some other non-Floridian white male, wins the nomination this time, and they want a Hispanic running mate, Rubio has a shot at the #2 spot on the ticket. But that's more likely to happen if he's not in the middle of running for reelection for Senate.