Uh... I can think of a couple of explanations for this, though they seem a bit too rational to credit to this guy, tbh.
One is that I think Florida has closed primaries. Being a registered Democrat would let him vote in the Democrat primaries, and then he can just vote Republican in the general. I know some people do that.
That's why you register unaffiliated. At least in my state you can vote in both parties during the primaries
---Cid- "looks like that overgrown lobster just got served!" Bartz-"with cheese biscuts AND mashed potatoes!"