By Major Garrett

A new Des Moines Register poll in Iowa shows Barack Obama leading the Democratic presidential primary race just two days out from the first-in-the-nation caucuses, but the accuracy of the poll is in question because the survey was taken during a time of year when poll respondents are preoccupied with year-end activities.

Still, the telephone survey of 800 likely Democratic caucus-goers taken Dec. 27-30 shows Obama outside the margin of error for the first time with 32 percent of respondents supporting him. That's up from 28 percent in the Register's last poll in late November. Hillary Clinton received 25 percent and John Edwards was at 24 percent, virtually unchanged from the last poll by the newspaper. None of the other candidates get more than 6 percent of the vote.

Click here to read the Des Moines Register poll story.

While a third of respondents said they could still change their minds before Thursday's caucuses, the poll will have some effect because it will shape early TV and radio coverage. Late-deciders look for a whiff of victory and this poll will tell fence-sitters Obama might win. That impression could make undecideds more comfortable with the idea that Obama could win and that idea alone could move people to Obama.

One part of the psychology in the primary races for late-breaking voters is the sense that someone could win and they want to be with the winner. That phenomenon helped John Kerry considerably in 2004.

But, Iowa is a strange environment. The Register poll hits New Year's morning, among the lowest readership days on a newpaper's calendar. Similarly, TV viewing and radio listening will be far lower than on a typical day. The Register's poll may not have the impact as it had in years past and could have this year if it fell on a day other than New Year's Day.

Also, methods matter in polling and some trepidation exists at the Register internally over these numbers. The numbers do not track with other recent post-Christmas polls. Polling between Christmas and New Year's is extremely slippery under the best of circumstances, which these are not.

Likely poll recipients are tired of nagging poll calls, campaign calls, robo-calls and special interest calls. Households on Democratic Party lists get five to six calls a night right now.Also, in polling the assumptions matter.

Polling is a science and an art. The science part is building a model for survey gathering and data synthesis. The art part is balancing variables such as turnout, likely sub-group representation and participation, for instance, men, women, young, old, first-time caucus-goers, caucus regulars, labor union members, etc.

So, when a poll like this one shows 60 percent of caucus-goers are likely first-time attendees, questions automatically arise. For example,  has first-time turnout ever been that high? Answer: No. Has it ever happened before that 40 percent of Democratic caucus-goers will be independents and 5 percent will be Republicans, like the poll says? Answer: No. In 2004, Democratic turnout was 80 percent.

Clinton pollster Mark Penn disputed the results in a blog comment posted on the campaign Web site."The Des Moines Register poll this time has 40 percent independent voters and 5 percent GOP voters in the poll when past independent participation has been 15 percent in 2000 and 19 percent in 2004, and the GOP has generally made up 1 percent of the vote.

So they are depicting an unprecedented departure from historically established turnout patterns in the caucus. Under their model, only 55 percent of the caucus-goers would be Democrats," Penn wrote.  "The other recent polls all show Hillary trending up and leading or within 1 point of the lead, and many show her moving up from a substantial deficit to tie and having the momentum in this race."And the New York senator's communications director told FOX News he's not buying them. "There are two other polls out there this morning ... that have Senator Clinton with leads," said Howard Wolfson. "I'm confident that we're going to do well and we're going to give everything we have in the next several days to get our supporters out. We feel like we've got the wind at our backs here and not just because of the weather. ... We've got a great operation here, the best I've ever seen."Click here to watch Howard Wolfson on FOX News.

The Democratic caucuses in Iowa are first and foremost a party-building exercise. It's designed to attract hard-core party activists and those willing to partake in scut work throughout a hard-fought election year. That's why turnout is low.

Iowa has 700,000 registered Democrats. On caucuses night about 150,000 will participate, a small fraction of registered Democrats.

So, if a party-building exercise fails to attract even a majority of registered Democrats, it's hard to imagine a huge number of independents and Republicans will play ball.

Wolfson said he also thinks Clinton's campaign can withstand not taking a definitive first place in Iowa.

"We've always prepared our campaign to run this for the long haul. ... If there's a three-way tie here, the race and the nomination continues," he said.

Many other possible trapdoors exist in the data, but for now all three leading campaigns see them as danger signs in the believability of the Register's numbers. Even so, Obama's campaign said it will take the results.

"It's a good way to ring in the new year," said Communications Director Rob Gibbs.