Here is why a win in Iowa means something for Obama and means nothing for Huckabee.
The race in New Hampshire, for the Democrats, is essentially the same as it was in Iowa. Turn out of independent voters is wicked important. Only old, stanch Democrats show up, it's a close race between Obama and Clinton. Young independents show up, Obama runs away with it. So Obama doesn't have to change anything, theoretically, to repeat his success and any negativity on Clinton's part is only going to hurt her. See below — it's now the American dream vs. Hillary Clinton and she can't win that.
For the Republicans, Iowa was a race to see who the Christian Right would choose as their candidate, but it ignored the other half of the Republican party, the neo-con, fiscal conservative wing that could really care less about where you go to church. Romney was supposed to be able to get broad support from both wings and wasn't able to snag the Christians because of his Mormon underpants and, well, he sort of comes across as a pompous ass. Huckabee, although he may have the support of the Right Wing Christians who think that the only thing that matters in America is some imaginary woman's uterus, has no support in the neocon, fiscal conservative wing because, well, he's not a neocon or fiscally conservative. Huckabee will not be able to change that in the next month which means, without some brilliant southern strategy, he's done. The Republican who will win the nomination is the one who can appeal more to both of these sides than anyone else. Just having the support of one wing isn't going to be enough.
I predict McCain/ Huckabee v. Obama/ Biden in the fall with Obama/ Biden winning big.