By Major Garrett

For those watching Iowa closely, the rise of John Edwards in the past week has important consequences going forward.An Iowa win for Edwards is possible. He has pulled into a virtual tie with Hillary Clinton and Barack Obama in all the post-Christmas polling. A Mason-Dixon poll of 400 likely Democratic caucus-goers sampled from Dec. 26-28 found Edwards with 24 percent compared to Clinton with 23 percent and Obama with 22 percent. Bill Richardson polled at 12 percent in the poll, and undecideds formed 8 percent of the sample.Of course, holiday time polling is frequently unreliable and caucus polling is tricky under the best of circumstances, but that doesn't mean the polling data doesn't capture trends. It can and often does.

Edwards' trajectory is up. All the campaigns agree on this. He is the only candidate who has competed in Iowa before and the only one with organizers who've demonstrated an ability to cut deals on caucus night to garner support from candidates who don't meet the 15 percent viability threshold. For instance, in 2004, supporters of Dennis Kucinich went for Edwards, propelling him into second place. He later became the vice presidential nominee.

Edwards also has more people in more precincts -- 1,781 precincts in all -- than either Clinton or Obama. That gives him a structural advantage that Clinton and Obama both fear if turnout hits the 2004 total of roughly 125,000.

Edwards has increasingly drawn Obama's attention with heavy complaints about spending by 527 groups on his behalf. 527 groups are outside organizations collecting undisclosed and unlimited donations.

Speaking on CBS' "Face the Nation" on Sunday, Edwards said he has called for those groups to stop working on his behalf, but can't actually place a phone call because it would violate election laws against campaigns coordinating with private groups.

"I think they should be illegal. I've made that absolutely clear. I've said publicly numerous times now that I call on them to stop any ads that they're running," Edwards said. "I think if a candidate calls something running a 527 and tells them to either do something or not do something, that could be interpreted as a coordination. So what I did is the day I found out about this, I made very clear I'm against 527s. I didn't want them running advertising, and I've continued to say that every time I've been asked. But I can't stop these people, Bob. I don't have control over them."

As the Iowa caucuses close in, Obama's closing stump speech contains anti-corporate riffs that sound a tad more aggressive than before and a new riff that appears to be a response to Edwards' indirect charge Obama is too soft and conciliatory to achieve real "change."

These tactical maneuvers from Obama suggest real concern about Edwards' rise, something senior Obama advisers concede.

Why the concern? An Edwards win might mean Obama finishes third with Clinton in second. A Clinton win with Edwards a strong second would also relegate Obama to third. Third isn't catastrophic for Obama, but it's very bad.

Of the top three candidates running in Iowa, only Obama has a strategy that relies to a significant degree on brand new caucus-goers. If he pulls it off, he will not only win Iowa but give legitimate rise to a new kind of inclusive politics.

But the smashed wreckage of campaigns that sought "new and improved" over tried and true strategies is a recurring theme in presidential primaries. This is hard work and caucus politics are highly personal, highly structured, intimidating and knee-deep in party building activism. In other words, they aren't user-friendly to the novice.

When Edwards was polling a few points back in the race, the Clinton-Obama, Obama-Clinton narrative was both simple and compelling. While it is tempting it is dangerous to stick with this familiar story now.

But if the narrative has changed, several questions arise.

If Edwards can win, why isn't Clinton attacking him? Tactically, the Clinton campaign believes she can withstand an Edwards victory more than an Obama victory because she has better infrastructure in New Hampshire and far more money, and can attack Edwards where he is still third though closing in on Obama. With this strategy, Edwards takes a portion of the anti-Clinton vote away from Obama and puts it in his more "beatable" basket.

Would an Edwards win in Iowa propel him to victory in New Hampshire or elsewhere? It is doubtful because he lacks resources and organization downstream. An Edwards second place finish would almost surely eliminate all hopes of winning the nomination because it would deprive him of any slingshot to New Hampshire. But an Edwards victory would introduce a new variable to the race. Clinton would have to train her sights on him and Obama would have to fight hard to regain the "change" label. An Edwards win would also give him a massive burst of publicity and media coverage (along with the scrutiny, of course) that would provide a net lift. He willl still lack money and ground forces, but he would have at least a puncher's chance in the Granite State.

Does Edwards' rise pose a bigger danger to Obama or Clinton?  Obama, because they both share the "change" candidate label? In Iowa, whoever is closest to Clinton, who is positioning herself as the "experience" candidate, will go to New Hampshire as the "change" alternative.

Edwards has injected "change" into his closing stump speech, saying if he wins there will "be a tidal wave of change" on behalf of anti-corporate fighters for universal health care, re-written trade laws and higher taxes on corporations and the wealthy. Edwards' close on "change" is aggressive, specific and tailor-made to middle-class Democratic anxieties about the economy.  As Edwards has honed this message, his support has grown -- another trend to consider.