Clearly, Huckabee did systematically better than Santorum, although a few of these are inside the margin of error. Romney’s advantage was that the rest of the 2008 Huckabee vote was spread across Michele Bachmann, Newt Gingrich, and Rick Perry.
Thus, Iowa is a metaphor for the whole 2012 Republican nomination campaign. It is not as though Mitt Romney has increased the breadth or depth of his support relative to 2012. At least not yet. Instead, his advantage is due primarily to the weakness of his opposition.
After all, not only did Romney lack a credible challenge from his right in Iowa, he is essentially unchallenged from his left, unlike in 2008 when he had to contend with Rudy Giuliani and John McCain. Next week in New Hampshire looks to be a total rout, in no small part because there is no John McCain-style candidate in the New Hampshire race.