These are nice numbers for Roxanne Conlin, who is still unknown to 20% of likely vteros. However, R2K's polling (including their first poll of this race for Daily Kos) has really bounced around a lot. In October of last year, it was Grassley +12, then Grassley +21 in February, and now Grassley +9. I'm not really sure there's an explanation for this gyration. (And as far as I understand, R2K used the same methodology for both clients - and you can see that the question wording is the same, too.)
IA-Gov:
Chet Culver (D-inc): 41 (38)
Terry Branstad (R): 48 (54)
Undecided: 11 (8)
Chet Culver (D-inc): 44 (41)
Bob van der Plaats (R): 40 (38)
Undecided: 16 (21)
Chet Culver (D-inc): 46 (48)
Rod Roberts (R): 36 (26)
Undecided: 18 (26)
(MoE: ±4%)
Again, a lot of bouncing in the toplines: Branstad +5 to Branstad +16 to Brandstad +7. The latest survey is good news for Culver, sure, but that's a bit like saying Dukakis did better than Mondale - the numbers still suck.