Grayson and DWS will lose. Both are too partisan and are only in congress because their districts were drawn specifically for them.
It's not as if Mr. Rubio is terribly unpopular, or scandal-ridden, or anything of the sort. Democrats need Murphy or Graham to win, and that's a fact. (Heck, I'd be willing to vote for either one, as they're both in the more conservative side of the democratic party, and Rubio's hardly some moderate stalwart and is willing to flip-flop solely for political gain.)
So, a partisan Republican can win a U.S. Senate seat but the same is not true of a partisan Democrat?
Yes, because Rubio's good at coming off as more moderate than he is to the uninformed, because of incumbency, because he's not a raging socon, and because FL still has a republican lean, even if only a slight one, outside of presidential elections