I'm actually shocked because it is such a risk. It's still quite possible Rubio loses this thing to Patrick Murphy, in which case that severely hurts Rubio's political career. It doesn't make sense to me because clearly his ultimate goal is to be president, and he could've launched a 2020 or 2024 campaign without being an incumbent senator.
I mean for the GOP it's alot better then the current options running against Murphy. And with Rubio running again he would have a modest advantage.
For Rubio it's also alot easier then running against Bill Nelson or for Governor in 2018 no matter how good the political enviroment is.