Mason-Dixon for Ron Sachs Communications (2/9-10, registered voters, March 2010 in parens):
Bill Nelson (D-inc): 41 (35)
Jeb Bush (R): 49 (50)
Undecided: 10
Bill Nelson (D-inc): 45
Connie Mack (R): 40
Undecided: 15
Bill Nelson (D-inc): 49
George LeMieux (R): 35
Undecided: 16
Bill Nelson (D-inc): 48
Mike Haridopolos (R): 27
Undecided: 25
Bill Nelson (D-inc): 46
Adam Hasner (R): 24
Undecided: 30
(MoE: ±4%)
I've seen better, and I've seen worse. Obviously the Jeb Bush numbers are concerning - even though he's exceedingly unlikely to run - but the trendlines (which are extremely old, and reflect a poll taken at the height of healthcare reform in the news) show some improvement for Nelson. It's not the amount of improvement that interests me but the fact that improvement is even possible. If the economy picks up, if Barack Obama contests Florida, and if general anti-incumbent-party anger continues to fade, Nelson's numbers could get better still.
I also like the fact that he isn't locked into the low 40s. Sometimes you see these really troubling polls where the incumbent is matched up against everyone ranging from Republican Jesus to Some Dude and he gets 40% regardless of his opponent's name rec. Nelson does better against lesser-known opponents, which to me suggests there are some potential Republican voters who are still willing to give ol' Nellie a chance. (Note that this squares with something PPP found a few months ago.)
There are a couple of other potential names in the mix that M-D didn't try - wealthy third-term Rep. Vern Buchanan, and probably-dreaming freshman Rep. Daniel Webster - but I suspect their numbers would look something like those of the two least-known candidates, at the bottom of the list. If you need a refresher, Mike Haridopolos is the state Senate President (and is the only candidate who is actually more-or-less officialy in the race), while Adam Hasner is the former state House Majority Leader.