Clinton will win reelection in 2020 over Gov Rubio of FL.
If Rubio goes for FL-GOV in 2018, I'd take it as an indication that he's less likely to run for President in 2020.
He'd already have a high-enough profile after running in 2016 to justify a run in 2020, taking-on being governor of the 3rd largest state would detract from his ability to be fully committed to the presidential campaign trail. Plus, there would be significant overlap (and thus redundancy and inefficiency) preparing for a gubernatorial run in 2018 AND a presidential run in 2020.
Plus, incumbent Presidents are hard to beat. Rubio would more than likely be angling for a run in '24 or '28 if he's going for the governorship in 2018.
