Why do people think Bill Nelson will be difficult to beat? What's his claim to fame other than being an astronaut? I think Catherine Harris has as good a chance as anyone at knocking Nelson off, especially if the President, Rove, and Jeb get behind her.
Nelson has "fed" enough interest groups to create issues.
Nelson, for example came out in support of boy scouts once. (only once that I know of)
He also is a member of the old political elite and has enough inside conections with unions. This is much like Lawton Chiles (despite his effort to change the FL constitution to impose an income tax) and Gov/Sen Graham (despite his loosing it otherwise).
It would be folly to NOT see Nelson as a strong candidate. He has not any fatal mistakes.
The candidates who stood a chance of beating nelson have bowed out.
It is why I think his FMA vote can be used against him.