I'm not surprised to see these post-debate poll numbers out of Iowa, and I wouldn't be surprised if further results from other pollsters reaffirmed them, especially Gingrich's slide:
Gingrich has dropped 5 points in the last week and he's also seen a significant decline in his favorability numbers. Last week he was at +31 (62/31) and he's now dropped 19 points to +12 (52/40). The attacks on him appear to be taking a heavy toll- his support with Tea Party voters has declined from 35% to 24%.
Paul meanwhile has seen a big increase in his popularity from +14 (52/38) to +30 (61/31). There are a lot of parallels between Paul's strength in Iowa and Barack Obama's in 2008- he's doing well with new voters, young voters, and non-Republican voters
This fits with what I saw in Iowa last weekend, and I think it's the beginning of a Gingrich collapse. His main virtue in the eyes of GOP voters is that he's the most electable non-Romney. Now he's within the margin of error of Romney and Paul, while Perry is rising. I bet plenty of Bachman and Perry supporters who were contingently settling for Gingrich, are now going home to their original candidates.
And, also as I wrote in my column, I expect Paul, at caucus, to outperform whatever his poll results are (though I bet this Paul result of 21% is a bit higher than other polls will show).
The poll cited above was a Public Policy Polling survey of 555 likely caucus-goers with a margin of error of +/- 4.2%.