Hummm, before Poblano became the 'corporate geek' Nate Silver, he was writing some political tech analysis (right here at the Orange Satan!) that was so good it became legend.
New Hampshire polls are a leading indicator to national polls. Voters are more engaged and more informed in New Hampshire than they are nationally. As the primary season progresses, voters continue to become better engaged and informed, until the actual voting takes place, when the voters are presumably as informed as they ever will be.
In other words, if a candidate is doing better in New Hampshire polls than he is in national polls, that suggests that as voters become more informed, they will continue to slide toward that candidate. At so the candidate will do well in the voting booth, at which point all voters are highly informed (relatively speaking, at least). On the other hand, if a candidate is doing better nationally than he is in New Hampshire, that suggests that the candidate may not hold up to scrutiny, that he may be trading primarily on name recognition, etc. His support is superficial.
The litmus test of this then becomes Iowa. If a candidate is doing better in New Hampshire polls than he is in national polls, and that candidate does well in Iowa, that provides very powerful evidence that this increase in information works to the benefit of that candidate.
You might call this something like "the momentum of information". This hypothesis, by the way, has been confirmed by other researchers.
Poblano was referring to applications for 2008 and we all know how that turned out.
Presently in the Democratic race, we are seeing a pattern wherein Barack Obama is doing better in Iowa than he is in New Hampshire, and better in New Hampshire than he is nationally. This is a very favorable alignment of the numbers. It is so powerful, in fact, that I believe it may explain the shift in tactics from the Clinton campaign.
Check out Nate's 2007 piece, it's fascinating. Is history repeating itself?