Iowans will cast the first votes in the 2016 presidential campaign in 29 days.

A half dozen candidates were in the state during the last week of 2015. Bernie Sanders even spent New Year’s Eve here, speaking briefly to about a thousand supporters.

“We together have an opportunity to make 2016 a year that history will long remember,” a very hoarse Sanders said during brief remarks.

Two candidates returned to the Iowa campaign trail January 2.

“Happy New Year to everybody,” Republican Mike Huckabee said to about two dozen people gathered early Saturday morning at the Northside Cafe in Winterset.

It was the first of 150 events Huckabee plans to hold in Iowa during the month of January and he declared the race “wide-open.”

“Historically, over the past two election cycles there’s been a 20 point swing in the last 30 days leading up to the Caucus. The front-runner 30, 40 days out was never the winner,” Huckabee told reporters.

Huckabee said he’s putting in the time because he believes “retail” politics can still work in Iowa and the majority of likely Iowa Caucus goers haven’t made up their minds.

“Last time I checked, nobody’s voted yet,” Huckabee said.

Democratic candidate Martin O’Malley began his Saturday with an event at the West Des Moines Public Library that attracted about 100 people.

“This is my first event of the new year,” O’Malley said, to laughter from the crowd gathered in a meeting room of the library.

O’Malley cast himself as a true blue Democrat during his remarks, a way of striking a contrast with Sanders, who is a Democratic Socialist, and Hillary Clinton, who switched from being a Republican to being a Democrat while she was in college.

“Look, my own story is not a story of Democratic conversion. It’s more a story of Democratic upbringing. I am, in fact, the only life-long Democrat seeking the Democratic Party’s nomination this year,” O’Malley said, to applause.

O’Malley, at the close of his half-hour appearance, said Iowans have the opportunity to “surprise” the pundits by choosing an “alternative” candidate.

“I think psychologically a lot of Iowans put off making a commitment until after Christmas and now that Christmas is past and people are entering now that ‘decision envelope’ and making up their minds,” O’Malley told reporters afterwards.

The candidates’ dash to the Iowa Caucuses will get more crowded Monday. Ted Cruz will be in Boone Monday morning to kick off a week-long bus tour of the state. Hillary Clinton will be in Davenport, then make stops in five other cities before exiting the state Tuesday.

“I’m not taking anything for granted. I expect this to be competitive until the end,” Clinton told Radio Iowa during a telephone interview Sunday. “…We’re going to run hard and do everything we can to make sure people turn out and bring family members and friends.”

Clinton praised the Iowa Democratic Party for scheduling a “tele-Caucus” for Iowans who are out of state on February 1, plus scheduling some satellite caucuses at job sites for shift workers who can’t get the whole night off.

“The party has taken some important steps forward and we will evaluate how much more access that provides to people who have the desire to participate,” Clinton said. “But I applaud the steps that the party has taken to try to broaden the universe of caucus participants.”

How many Iowans will choose to be participants in the Caucuses? That’s the question each campaign is trying to answer.

“First, we know people who normally don’t caucus don’t caucus,” said David Redlawsk, a former University of Iowa professor who is now a fellow at the Harkin Institute at Drake University. “Secondly, if they’re going to caucus, it’s usually because a campaign’s reached out and has pushed.”

That’s what appeared to happen in 2008. There were about 60,000 newly registered Democratic voters on caucus night compared to about 7000 new Republican voters. Both parties had record turn-out eight years ago. Redlawsk conducted a telephone survey of Iowans who attended those 2008 Caucuses.

“About 28 percent of those folks told us they considered themselves to be independents,” Redlawsk told Radio Iowa during an interview. “Even though they had to caucus on one side or the other, they don’t think of themselves as partisans.”

Caucusing is outside of many people’s comfort zone. Democrats literally have to stand in “preference groups” to indicate which candidate they support. Republicans get a straw poll ballot to fill out, so it’s a little less daunting, but they have to sit through a 15-to-30-minute organizational meeting first.

“I think the way the dynamics are working right now that independents may be more likely, if they come out at all, to be coming out on the Republican side,” Redlawsk said. “Just a huge amount of attention there, much less on the Democratic side.”

Sue Dvorsky, a former chairwoman of the Iowa Democratic Party, is a volunteer on Hillary Clinton’s campaign.

“When you’ve been with a candidate since the spring, this is what everything comes to,” Dvorsky told Radio Iowa as she worked the crowd at a recent Clinton campaign event in Keota.

According to Dvorsky,  it’s hard to tell which candidate on either side has the most robust “ground game” to turn voters out on Caucus night.

“That’s super exciting,” Dvorsky said. “As a person who is very, very committed to one campaign and deeply in it, it’s incredibly nerve-wracking.”

Paul Tewes, the state director of Obama’s 2008 Iowa Caucus campaign, said a candidate must build a credible campaign network to succeed in Iowa’s Caucuses.

“The saying always is: ‘They will come for the candidate. They will stay for the campaign,'” Tewes told Radio Iowa during a telephone interview.

Tewes said Obama was wiling to start spending the money to establish “organizational muscle” in Iowa 10 months before the Caucuses. That paid staff spread around the state made a “deliberate” effort to talk to Republicans and independents.

“Because I think we had such a big and robust organization and real estate everywhere, people felt comfortable engaging in a conversation with the campaign,” Tewes said. “You know, it’s not something that can be turned on overnight. You have to build a comfort level with these folks.”

Tewes called caucusing a “physical process” and he expressed his doubts that an email, a text or a Facebook post can replace the kind of one-on-one campaigning that yielded results in 2008.

“It’s still old-fashioned shoe leather and it always will be,” Tewes said. “I mean candidates that haven’t invested in that are probably going to wake up the morning after the Caucuses and say: ‘Why didn’t we do that?'”

Eric Woolson helped lead Huckabee’s successful 2008 campaign, which at the very end of the campaign had just a dozen paid staff. During a New Year’s weekend appearance on Iowa Public Television’s “Iowa Press” program, Woolson cited the impact of energetic campaign volunteers on Huckabee’s successful 2008 campaign.

“When you’ve got people walking through the door. When you’ve got people that say, ‘I want to sign up. I want to do something. Don’t just put my name on your list of supporters,'” Woolson said, “‘but give me something to do.'”

Brad Anderson managed President Obama’s 2012 reelection campaign in Iowa, but he also worked on John Edwards’ 2004 Iowa Caucus campaign.

“The size of your organization, really, it’s kind of tough to see from the outside,” Anderson said during an appearance on the same edition of “Iowa Press” on IPTV. “But you know it on the inside.”

According to Anderson, the presidential campaigns are now testing their staff and volunteers.

“They’re going to be doing dry runs. They’re going to get staging locations. They’re going to be doing all the things they have to do to test their organization for that last four days,” Anderson said, “and that last four days leading up to the Caucuses is all about turnout.”

Woolson expects candidates who’ll spend campaign time in the state this month will fare better than others.

“I think a lot of folks are going to decide awfully late and they will move around, but I think that a lot of the support for Cruz and a lot of the support for Trump is solid,” Woolson said. “It’s going to stay there.”