With one month to go before the 2008 Iowa caucuses, the leading contenders for both the Democratic and Republican nominations are running neck and neck in the state and battling for the support of Iowa voters.
The first-in-the-nation Jan. 3 caucuses are poised to shake up what has been an extraordinary presidential race — one that started earlier than any other, and with more intensity and more money being spent on both sides.
"This is clearly the biggest race we've seen in years," said David Yepsen, longtime political columnist for The Des Moines Register.
Statistical Dead Heat
The leading Democratic presidential contenders are locked in a three-way battle in Iowa with Sen. Barack Obama of Illinois the preferred choice of 28 percent of likely caucus-goers, New York Sen. Hillary Clinton at 25 percent support and former North Carolina Sen. John Edwards at 23 percent, according to a Des Moines Register poll released this weekend.
The Des Moines Register poll closely resembles a November ABC News/Washington Post poll that found Obama and Clinton in a statistical dead heat, with Edwards following closely behind.
Both polls indicate a wide gap between the top three Democratic presidential hopefuls and the remainder of the field.
Democrats Sharpen Strategy, Rhetoric
With an influential Iowa caucus win at stake, the candidates are pouring time, money and resources into Iowa, and sharpening their rhetoric against one another.
Clinton's campaign has dispatched hundreds of staffers and volunteers to the state, and has organized a get-out-the-vote team to urge people to the caucuses.
The campaign has increased Clinton's appearances in the state and those of her husband, the popular former President Clinton.
This week the campaign unveils a "Take Your Buddy to Caucus" push to urge more people to get involved on Jan.3.
"We know we have a lot of work to do to get people out to vote and to make sure they stand in front of their friends and neighbors and caucus for Hillary," said Mark Daley, Clinton's Iowa communications director.
The campaign has also produced a humorous "caucusing is easy" video featuring Hillary Clinton attempting to sing the national anthem and Bill Clinton eating a cheeseburger to illustrate that singing and exercising may be hard, but caucusing is easy.
Getting Out the Vote
The Obama campaign is also marshalling resources in the Hawkeye State, launching an interactive online caucus center on its Iowa Web site, explaining the caucus process and directing voters to their local caucus site.
Obama's Iowa effort is getting some celebrity star power Saturday when Oprah Winfrey campaigns with Obama and his wife, Michelle Obama, in Des Moines and Cedar Rapids, Iowa.
"He's going to spend more time in the state and talk about his vision for bringing change to Washington, D.C.," said Josh Earnest, Obama's Iowa spokesman.
In a move that is legal, but politically risky, Obama's campaign has distributed 50,000 brochures on Iowa college campuses telling college students they can caucus for him even if they aren't from Iowa.
Many students who attend college in Iowa are from Obama's neighboring home state of Illinois — something that could give Obama an advantage considering his strong support among young voters.
The Clinton campaign angrily denounced the strategy this weekend.
"The Iowa caucus should be for Iowans," it said.
"Rather than denigrating the caucus rights of students who go to school in Iowa, we would suggest the Clinton campaign organize them," Obama campaign spokesman Bill Burton fired back in a statement.
Edwards, who came in second in 2004 in Iowa to Sen. John Kerry, D-Mass., has campaigned across the state with his wife, Elizabeth.
Edwards campaign strategists say they have a strong base of supporters in almost every precinct in Iowa, and are busily wooing new supporters as well.
"What really matters is — I learned very up close and personal in 2004 — is what happens in the last 30 days," Edwards said while campaigning in Fort Dodge, Iowa, Sunday. "It's when people start making decisions."
The front-runners aren't the only Democrats mobilizing in Iowa.
Long-shot Democratic presidential candidate Sen. Chris Dodd of Connecticut has moved his family to Des Moines, Iowa — including his two young daughters — in order to campaign around the clock.
Slightshot to the Nomination
Many candidates are throwing everything they've got at the Hawkeye State, knowing the caucus could make or break their presidential bids.
"A win in Iowa can take an obscure candidate and slingshot them to the nomination or, in the case of [Jimmy] Carter, clear all the way to the White House," Yepsen said.
Iowa's political clout has been a magnet for candidates and the media since 1972, when a surprise Iowa caucus win boosted George McGovern's presidential campaign.
While a surprisingly strong showing in Iowa helped Jimmy Carter in 1976, far more candidates have found their White House aspirations squashed after the early votes.
Winnowing the Field
Iowa has historically had the function of crushing the presidential aspirations of some — winnowing the presidential field for the rest of the nation.
"In the history of these caucuses, no candidate who has ever finished worse than third among the candidates has even gone on to win the nomination," Yepsen said.
"There are three tickets out of Des Moines to Manchester — first class, coach, and standby," he said.
But for the Democratic contenders, being the second choice of Iowa voters could be as important as being their first pick.
Under Iowa Democratic Party rules, in most of the almost 2,000 precincts across the state, each Democratic candidate must draw at least 15 percent support.
If that fails to happen, their supporters have the opportunity to throw their votes to a more viable contender.
That could be a crucial disadvantage for some candidates.
Obama is the second choice of 26 percent of likely Democratic caucus voters in Iowa, while Edwards is the second choice of 24 percent, and Clinton is the second choice of 19 percent, according to the November ABC News/Washington Post poll.
Clinton strategists say they are working hard to close the gap between the senator and her leading rivals.
"We want to be everybody's first and second choice," Daley said.
Huckabee vs. Romney
The Republican caucuses in Iowa don't have a viability threshold. There, every caucus-goer gets one vote, no matter whether their neighbors support the candidate or not.
Former Gov. Mitt Romney and former Gov. Mike Huckabee are in a statistical dead heat in Iowa.
Romney's campaign has invested millions of dollars in television advertising and organization in Iowa, leading polls there for months and winning the nonbinding Iowa Straw Poll in August.
But in recent weeks, Romney has faced serious competition in the state from underdog Huckabee, who has 29 percent support of Republican likely caucus-goers to Romney's 24 percent support, according to the Des Moines Register poll.
First With the Most
The Iowa front-runners have vastly outpaced former New York Mayor Rudy Giuliani — the national GOP poll leader — as well as former Tennessee Sen. Fred Thompson, Arizona Sen. John McCain, and Texas Rep. Ron Paul.
The Huckabee campaign is busily trying to downplay expectations for the surprise leading Iowa contender.
"Gov. Romney has gotten here first with the most," said Eric Woolson, Huckabee's Iowa campaign manager.
"He's got the organization, he's got the staff, he's got the advertising and the people, and there's always, always been this sense that Iowa is his to lose," Woolson said. "What we're trying to do is make sure that we're in the Top 3."
While a win in Iowa can be important, other candidates may be banking on New Hampshire, which holds its first-in-the-nation primary Jan. 8.
"Both Giuliani and McCain have effectively pulled out of Iowa and really aren't doing that much here, just sort of token efforts," Yepsen said, noting both candidates are spending more time and advertising money to New Hampshire.
"In sort of clearing the field for Huckabee, they hope to wound Romney here [in Iowa], which will make their task in New Hampshire a whole lot easier," he said.
While McCain has yet to gain traction in Iowa, he has won the backing this weekend of the New Hampshire Union-Leader, an influential media endorsement that may boost his campaign in the first primary state.
Making a tight race even more unpredictable, more than 50 percent of likely caucus-goers who said they had a preferred candidate also said they could change their minds, according to the Des Moines Register poll.
However most caucus-goers have narrowed the candidates down to their Top 2 choices, said Iowa resident Tina Kastendieck, a GOP precinct captain.
"We've seen the candidates in person so many times that I don't know anyone who hasn't made up their minds yet," she said. "Most people I talk to are down to their final two, and they would be happy if either of them get in."
ABC News' David Chalian, Kevin Chupka, Eloise Harper, Raelyn Johnson, and Sunlen Miller contributed to this report.