Rubio could still help a Republican carry Florida. That's still huge in the race.
Rubio's favorables in Florida are abysmal. He will hurt more than help.
But his favorables are great with Cubans, who voted for Obama in 2012 but have voted sometimes voted overwhelmingly Republican in the past (in 2004, a Republican Senate candidate won 50%-49%...while carrying Miami-Dade County, even as he ran far behind normal Republican numbers in the rest of Florida). Rubio still has more up- than downside in Florida.
This.
Younger Cubans are trending toward the Democrats, but Rubio is one of them. And he's a MIAMI Cuban, with an experience MUCH different than Ted Cruz or his parents.