Rubio will find a hard time in the primary. He is intensely disliked by many for his duplicity in supporting the Gang of 8 bill and taking a lead role. You can bet he will seek Trump’s backing if he decides to run. Even then, he will be challenged.
He already has had Trump’s backing - Trump has been urging him to get back into the race.
I actually don’t think he should - it would be best for him to take a break from politics...either temporarily or permanently.