Historically, the national polls and even the New Hampshire polls are largely meaningless because the results in Iowa will radically change the landscape for all the candidates. Here is
the best analysis I have seen on the phenomenon:
In late 2003 the Kerry campaign made a radical decision: it decided to close most of its New Hampshire campaign and bet everything on Iowa. It's not an often discussed decision, but it remains the best tactical decision I have ever seen a campaign make during the primaries. It was based on the fact that national polling is irrelevant before Iowa, and to some extent so is New Hampshire Polling
What made the decision fascinating at the time is that Kerry's campaign manager was Jeanne Shaheen. While best known as a governor of NH, she is also without a doubt the master of the New Hampshire primary. She has run 3 winning NH campaigns: Carter in '76, Hart in '84 (where I met her) and Gore in '00. Obviously two of those races (Carter and Hart) represent some of the biggest upsets in recent political history.
What Shaheen knew was that Iowa would completely re-make the NH race. And so it did. The tables below show the polling taken before the Iowa results were known, and the impact Iowa had on the final New Hampshire results:
The difference between winning the Iowa caucus and coming in third, for example, may result in as much as a 20% shift (or more?) in the actual New Hampshire primary vote as compared to pre-Iowa-caucus polling in New Hampshire.
Clearly, the
Obama campaign realizes "If Barack doesn't win Iowa, it's just a dream," and the
Edwards campaign also understands the importance of the Iowa caucus.
This will be a very interesting race.