CHICAGO - You might think that after months of a seemingly endless string of debates, rallies, straw polls and other campaign events, voters in the nation's first state to select a Republican presidential nominee might have made up their minds, but this year Iowans have other ideas.

With less than three weeks until the Hawkeye State's caucuses and only one more debate left - Thursday night in Sioux City - the GOP race still appears wide open.

"In my 30 years in Iowa, I've never seen a race like this," said Enrique Pena-Velasco, a Des Moines, Iowa, businessman who has yet to decide which candidate to support.

"People here in Iowa like to get to know the candidates," he said. "It goes beyond the politics. It goes beyond the policies of their campaigns. We like to get to know them on a personal level, their family, feel out what they're like, get to have a deeper relationship with them."

According to a Wall Street Journal/NBC News poll released Tuesday, Republican voters favor Newt Gingrich by a sizable margin. The former House speaker enjoys 40 percent support, compared to 23 percent for Mitt Romney and less than 10 percent for the rest of the candidates. But if Gingrich is to win the GOP nomination, then he will have to overcome a series of obstacles.

Thus far, the Republican race has seen four different leaders in the last five months. In addition to Gingrich and Romney, Rick Perry and Herman Cain have also sat atop the polls this year. Another candidate altogether, Michele Bachmann, won the first major test in Iowa, the state's straw poll in Ames, Iowa, last August. And still another candidate, Ron Paul, finished a close second in Ames and, according to most prognosticators, is now in a better position than Bachmann, Perry and Romney in the race for Iowa, to say nothing of Cain, who has suspended his campaign.

Part of the reason why Republican candidates have had such a hard time staying on top is because of the fact that the leaders of the race are forced to withstand a barrage of attacks from their rivals. In September, Perry quipped at a debate in Tampa, Fla., that he was taking so many hits that he felt like "a pinata." While Gingrich ably deflected his rivals' criticisms at last Saturday's ABC News debate in Des Moines, Iowa, the attacks don't only take place at debates.

"Gingrich might have defended himself well on the debate stage, but it may not ultimately matter. The barrage of ads that are running against him will make an impact on the race," wrote Craig Robinson on The Iowa Republican website this week. "His Republican candidates don't necessarily need to beat him up when they see him in person on the debate stage since they are spending millions of dollars beating him up on television. While Gingrich's fundraising has undoubtedly picked up as of late, it will be nearly impossible for him to be able to counter every negative attack that is out there."

"The best way for Gingrich to defend himself in advance of the caucuses is to aggressively campaign in Iowa," Robinson suggested. "There is no better way to deal with a slew of negative ads being run against you than standing in front of Iowans and taking these issues head on. There is no doubt that Gingrich is skilled enough to do it, the question is whether or not he is disciplined enough to do it."

The doubts about Gingrich - whether because of the "flavor of the week" nature of the GOP race or the candidate's infamous lack of discipline - may start to take a toll. A poll produced for ABC News by Langer Research Associates found that Gingrich has essentially the same unfavorability ratings as President Obama - around 48 percent - but a favorability score that is 13 points lower, meaning more are undecided about Gingrich than about Obama. In addition, Gingrich's core group of strong supporters is only half as large as the president's: 12 percent to 23 percent.

In the past month, the former House Speaker has actually become more unpopular among independents and Democrats alike, raising questions about his ability to win the general election. This past week, a University of Iowa poll, while not rated highly enough for air by ABC News, showed that Gingrich's support in the state had declined from its recent peaks, a trend that the pollsters cited as an indication that "his support may be starting to slide, as it has with previous frontrunners."

Other roadblocks lie ahead, too. In Iowa, the evangelical vote is key. In the 2008 caucuses, 60 percent of GOP voters identified themselves as evangelicals, a huge presence that propelled Mike Huckabee to victory there over Romney. The Arkansas governor secured 46 percent of evangelical support, compared to just 19 percent for Romney. To date, Iowa evangelicals have yet to rally around a single candidate, leaving a potentially major shift still up in the air.

Then there is the unique nature of Iowa's caucuses, a voting process that puts an emphasis on organizational power. With nearly 1,800 caucuses taking place across the state on Jan. 3, one candidate's superior organization can lead to a far higher voter turnout than a candidate who struggles to get out the vote.

The straw poll in August is seen as a test both of a candidate's ability to inspire enough passion in voters to win their vote and enough organizational might to get them to Ames, Iowa, but the poll's victor - Bachmann - has faded badly. However, Paul, the runner-up that day, has steadily placed in the top tier in Iowa polls. Plus, the Texas congressman only lost the straw poll by a scant 152 votes. And consider this: In 2008, the second-place finisher was none other than Huckabee, the eventual caucus winner.

With so much still up for grabs in Iowa, perhaps that is why every candidate except Jon Huntsman has elected to make a determined push for a caucus victory. Neither Gingrich nor Romney has spent a great deal of time there, but the former Massachusetts governor has a volunteer army engaging in door-to-door combat for him, and Gingrich has lately ramped up his operation in the state. Other candidates such as Paul, Bachmann, Perry and Rick Santorum have logged countless hours in Iowa over the past five months. Perry, in fact, just launched a whirlwind bus tour that, save a brief stop for Christmas, will keep the Texas governor in the state right up until caucus day.

Ultimately, as was the case with Huckabee, Iowa may not end up backing the eventual GOP nominee. Despite Gingrich's surge, Romney still retains the lead in New Hampshire. After the Granite State's primary, the race heads down south, where South Carolina and Florida will weigh in towards the end of January.

Earlier this fall, the Dixie swing was thought to be right in Perry's wheelhouse, but now it appears to be anybody's game. If the twists and turns that the election cycle has delivered over the last year are any indication, more surprises are likely in store.

"There is nothing predictable in this race," Pena-Velasco said with a chuckle. "Anything could happen."

Matthew Jaffe is covering the 2012 campaign for ABC News and Univision.