Pollster.com's Mark Blumenthal notes that there's a reason to be very skeptical about tracking polls taken of Democratic and Republican voters around the turn of the year: the sample will be skewed in myriad ways:
The first issue is that both Christmas and New Year's Day fall in the last two weeks before the Iowa Caucuses. Most pollsters prefer to avoid interviewing in this period because so many Americans are traveling, away from home or otherwise unlikely to participate in a survey. As should be obvious, any random sample will be representative of those who participate. If certain kinds of voters are less likely to be home and reachable during the holiday week, and if those voters have different political preferences than those more likely to be reachable, the results of the survey may be skewed.
And how is New Hampshire affected? Consider: the way that pollsters will pick up a surge of momentum from one candidate is to, well, poll... but given the intervening weekend -- Iowa will be held on Thursday, Jan 3 -- the rolling tracking polls wouldn't give an accurate picture of said momentum until Monday, Jan. 7 -- the night before New Hampshire -- and would, in any event, be skewed somewhat because of the nature of the weekend sample.
Here is something that Blumenthal may want to chew on.
Because the size of the voter pool in Iowa is tiny, and because, for Democrats, the caucus math is so complex, the campaigns themselves may find their own tallies of "1s" -- those folks who are almost certain to caucus for them -- are a better indicator of where things stand than any polling... the downside being, of course, that there will be no reliable way to compare their standing to that of their opponents, right until the night of the vote.
Then again, such a scenario is what the anti-polling crowd has always dreamed of: contests untethered to the influence of pre-election polls.
BTW: Blumenthal also has the latest data on one of my favorite problems in politics: the notion (empirically validated,to some extent) that polls, in late December, have much lower response rates than in any other month.