I think he pulls a lot of votes in FL. If his opponent surprisingly, "wins", and Rubio's own vote total is far less that earlier elections it will be noticeable.
They're going to need an obscene steal, like the 2020 general to pull it off.
If a new candidate runs instead of Rubio, with no past voting history, dems can make up any result they want.
That's my guess, anyway.