So it looks like there is news on this front; Nelson has gone from definitely not interested to seriously considering a run. Big Democrats are really pushing hard for a non-Crist candidate, and Nelson's certainly the best of the bunch. In my opinion a Nelson-Scott fight starts out as a very comfortable Likely Dem, a far better pick then Crist. I know how well beloved he is in North Florida; I know quite a few Republicans who would never vote for any Democrat except for him. I know I'd vote for him if I thought it was down to the wire.
http://politics.heraldtribune.com/2013/04/25/nelson-considering-running-for-governor/