In the small community of Boone, Iowa, about 100 people have crammed into the La Carreta — the only Mexican restaurant in town — to see Democratic Party presidential hopeful Andrew Yang fight for his political life.

He recounts being told the only way change could come to Washington would be if someone could create a political wave in other parts of the country and have it crash down on lawmakers' heads.

"The wave is you. The wave is this Monday," he said in reference to the caucus. "I stand before you today, fourth in the polls and rising to be the Democratic nominee."

His rise, however, might not be enough. While Yang is certainly not expected to win here, how he finishes on Monday night might just determine whether his campaign can survive.

If Iowa is the state where political momentum is built and candidacies are crowned, it can also be the place where they come to an unceremonious end.

In 2004, for example, Richard Gephardt, a national figure and former House minority leader dropped out of the race for the Democratic nomination the day after finishing poorly in the Iowa caucus.

"Caucus night becomes that moment where 'OK, it's reality that we're not going to win. And so do we still want to keep fighting or not,'" said Iowa State University political science professor David Peterson.

'Iowa is not first because it's important'

Every four years, this small state becomes a focal point of international media attention. It's the first state in the U.S. electoral process to name a party leader for president.

It may seem like a lot of fuss for a state that contributes just over 40 delegates out of around 4,000 to picking a party's presidential candidate.

Democratic presidential candidate former U.S. Vice-President Joe Biden speaks at a campaign stop at the National Cattle Congress Pavilion on Saturday in Waterloo, Iowa. (Andrew Harnik/The Associated Press)

But Dennis Goldford, a political science professor from Iowa's Drake University, said the reason is simple: "Iowa is not first because it's important. It's important because it's first."

"In any serial nomination process, whichever state goes first basically sets the parameters for what the field looks like," said Goldford, co-authour of The Iowa Precinct Caucuses: The Making of a Media Event.

It's the first time voters have a real, direct say over who they want to be the nominee, said Peterson.

The Iowa caucus has also become a pretty reliable indicator for determining who will become the party's nominee. Indeed, since 1976, almost every Democratic candidate who took Iowa faced the Republican nominee for president. The two exceptions were Michael Dukakis, who lost to Gephardt in 1988, and Bill Clinton, who lost to popular Iowa Sen. Tom Harkin in 1992.

But it was also here where an Illinois senator named Barack Obama gained huge momentum after claiming victory over Hillary Clinton, who finished third in the state.

'Less factional'

For Republicans, Iowa's powers to prognosticate the eventual party nominee have been more of a mixed bag.

It was certainly not an indicator in 2016, when Texas Sen. Ted Cruz defeated Donald Trump. Nor did it predict the eventual presidential candidate in 2012 when former Pennsylvania Sen. Rick Santorum defeated Mitt Romney — although just barely — or the GOP presidential candidate in 2008, when former Gov. Mike Huckabee defeated the eventual nominee John McCain.

Peterson said that's due to the more factional nature of the Republican Party in Iowa, which essentially includes three groups: evangelical Christians — who had backed Santorum and Huckabaee — the business class, and a smaller libertarian wing.

"For Iowa Republicans, it seems to be a little bit more of which group is ascendant in Iowa politics at a time. And that may not be the group ascendant in the party as a whole," Peterson said.

"The Iowa Democrats are, I think, less factional, it's a little bit less predictable who the main players are ... so they tend to gravitate to the candidate who does well nationally."

How Iowa gained its status

It was back in 1972 when Iowa started to gain its status. After 1968, both parties decided to open the system up and give voters more say in choosing delegates to the national convention.

But In Iowa, because of its complex caucus system, getting delegates to the national convention meant going through the process that included a state, district and county convention, along with precinct caucuses.

Because of all the stages and time involved in that process, Iowa would have to go first.

As former Des Moines Register political reporter David Yepsen recalled in a recent podcast, it was George McGovern and his campaign manager Gary Hart who decided to come to Iowa in 1972 when seeking the Democratic Party presidential nomination. McGovern, not the front runner or establishment choice, campaigned for three days and would place third.

Democratic presidential candidate Sen. Bernie Sanders and Rep. Ilhan Omar, far left, take a group photo with supporters at a campaign event at The Black Box Theater on Saturday in Indianola, Iowa. (Pablo Martinez Monsivais/The Associated Press)

He eventually secured the party's nomination, which helped legitimize the state's importance in the process.

Four years later, Jimmy Carter, a relatively unknown southern governor, committed a lot of resources into the state and placed second and eventually won the party's nomination.

"So historically, that's sort of where it started after Carter's eventual nomination. That became the playbook," Peterson said.

There have, however, been questions about how important Iowa remains, particularly in this election. It's not a "winner-take-all" state, meaning the delegates are awarded proportionally. This means, with so many candidates in the field, no one may really come on top.

Former New York mayor Michael Bloomberg, who entered the race late, is ignoring Iowa to concentrate on larger states. Back in September, the campaign of former Vice-President Joe Biden reportedly indicated that Iowa was not considered "a must-win" state and instead focused on Nevada, South Carolina and the Super Tuesday states.

'Why does Iowa get to go first?

In recent years, some have also questioned Iowa's first-place position in the nominating process. Critics complain Iowa, with a population that's about 90 per cent white, doesn't reflect the broader party, which relies heavily on diverse groups.

"I can imagine a scenario where a state that had a larger African-American and Latino community, candidates from those groups like Julian Castro or Kamala Harris or Cory Booker might be more viable and might still be in the race. And that's one of the concerns," Peterson said.

Goldford's response to that: Obama's Iowa victory.

"It was only when African-American voters around the country saw that he could actually win white votes that they started thinking maybe he did have a real shot."

Barack Obama waves to supporters at a caucus rally in Des Moines, Iowa, after winning the Iowa Democratic presidential caucus in January 2008. Surrounding him is wife Michelle, right, and daughters Malia and Sasha, bottom centre. (M. Spencer Green/The Associated Press)

Meanwhile, at a recent event in Fort Madison, Iowa, Biden told the crowd that he defends Iowa against those who believe it may be time for it to lose its first place positioning.

"They say 'Wait a minute, why does Iowa get to go first?' And I'll tell you what I tell them. Because you take it really, really seriously," he said. "You're going to winnow the field in who may in fact be able to be nominated president."

As a relatively rural state where advertising is not outrageously expensive, Iowa offers a political playing field where just about anybody, in theory, can build a successful campaign, Peterson said.

And when it comes to Iowa's importance, Goldford said there is a symbiotic relationship between candidates and journalists.

"As long as candidates think the caucuses are important, reporters will; and as long as reporters think the caucuses are important, candidates will."