Registered Republicans and Democrats in Iowa will head to their assigned caucus sites on Monday evening to participate in the anticipated early voting state's caucuses. Because of the unique voting process and because of its position as the first voting state after nearly a year of campaign wind-up, it draws perhaps outsized attention that goes well beyond the Hawkeye State. Although all the action begins promptly at 7pm CST, the caucuses might go well into the night, depending on just how convincing voters can be with their fellow caucus-goers – it's not just a 'cast your ballot' and go home kind of process.

How the Iowa caucuses work

Democrats and Republicans caucus differently, but both sides begin with local party business, including electing chairs and secretaries who head the night's proceedings, and a speech or plea delivered by the candidates or individuals representing them, according to the Des Moines Register.

Republican voters listen to the set of speeches and then cast their votes by show of hands or by ballot. With 11 Republican campaigns set to make thier case, the process could take significantly longer than in previous election years. On the Democratic side, participants physically congregate to show support for their top pick. Candidates may also place themselves in an uncommitted group. After an initial gathering period, supporters of each group are tallied and candidates with fewer than 15 percent of the vote are eliminated as "non-viable." Those supporters are then asked to realign with a different group in support of a different candidate or are recruited by one of the other groups.

Based on the night's outcomes, delegates will be assigned to represent the state at each of the parties' national conventions.

The Des Moines Register put this explanatory video together as a primer on how it all works:

The Republican field

For the win, all polling points to the two candidates atop the polls: Donald Trump and Ted Cruz. However, who wins the Iowa's GOP caucus – Trump or Cruz – might matter less than by how much. If Cruz loses by a significant margin, it may indicate he's lost party confidence after leading in Iowa polling just a few weeks ago. On the other hand, a Trump loss by evena handful of percentage points could reveal a crack in his persona as a winner, which could have effects on his campaign going forward.

But Monday's contest isn't just about who wins and who comes in second. It's also about which of the establishment candidates become viable should Republican voters on a national level determine they no longer want an outsider candidate like Trump or Cruz. Marco Rubio appears to have that position soundly locked up as a consistent third in Iowa. However, that could all change as Rubio barely stays in the top five in recent New Hampshire polling averages.

It's also an important test for two other candidates: Ben Carson and Jeb Bush. For Carson, who once led in Iowa in the fall, it could provide insight into how viable his candidacy is after a rough 30 days in which there was a shake-up among his top staffers and questions arose about his campaign's fundraising and expenditures, The Washington Post reported. And for Jeb Bush, Iowa will give him a sense of whether or not he can build momentum heading into New Hampshire, where he currently sits in fourth place in recent polling.

The Democratic field

What has been true in recent weeks remains true on the day of Iowa's Democratic caucus: Hillary Clinton and Bernie Sanders are neck-and-neck. According to most polling data, the two are in a statistical tie going into Monday's contest. Should Sanders win or be so close for it to be considered a tie, it would put immense pressure on the Clinton campaign, considering the Vermont senator's 15 point lead in the New Hampshire primary next week.

Clinton may be suffering from a case of déjà vu from her 2008 run in which she was expected to place second behind Barack Obama, but also fell behind John Edwards. In the last 72 hours, the Sanders campaign announced it had amassed $20 million in donations for the month of January, setting records of numbers of individuals who have contributed– more than Barack Obama's record in 2012, according to The New York Times. And news fell on Friday that nearly two dozen emails in Hillary Clinton's personal email account were deemed "top secret," according to the State Department, Politico reported.

The question for Martin O'Malley is: How much longer can he survive this beating? In Iowa, he sits at 4.4 percent – and that's his highlight thus far. In New Hampshire, O'Malley is at 2.9 percent and 2.2 percent nationally, according to RealClear Politics averages of recent polling.

What the numbers say

With all the endless polling – and the endless complaining by campaigns to go along with them – nearly all of them take seriously the final poll before the caucuses by Des Moines Register (with Bloomberg Politics this year) released Saturday evening.

Here's the breakdown among Republicans:

Donald Trump: 28%
Ted Cruz: 23%
Marco Rubio: 15%
Ben Carson: 10%
Rand Paul: 5%
Chris Christie: 3%
Jeb Bush, Carly Fiorina, Mike Huckabee, John Kasich, Rick Santorum: 2%

And among Democrats:

Hillary Clinton: 45%
Bernie Sanders: 42%
Martin O'Malley: 3%

If a single snapshot doesn't convince you, here are recent Iowa polling averages compiled by RealClear Politics for each of the GOP candidates: Trump (30.4), Cruz (24.2), Rubio (15.2), Carson (8.8), Bush (4.0), Kasich (2.6), Huckabee (2.6), Christie (2.4), Fiorina (2.4) and Santorum (1). And here are the recent averages for Democrats: Clinton (47.3), Sanders (44) and O'Malley (4.4).

Five predictions

Sorting out the conservative lane: "The Feb. 1 Iowa caucus is likely to bring an end to the con­ser­vat­ive-lane con­test. Ted Cruz is gaining momentum and seems to have the best organization, which is para­mount in try­ing to get voters out and stick around for two hours on a very cold Monday night. It is hard to see how the two pre­vi­ous Iowa caucus win­ners, Mike Hucka­bee and Rick San­tor­um, can stay in the race after get­ting shut out in the Hawkeye State," wrote Charlie Cook of the Cook Political Report.

Endorsements: Donald Trump said on Sunday that the lack of senators endorsing him will come to an end once he wins Iowa. "They will be very soon. You watch," Bloomberg reported. He also noted that Ted Cruz, a senator, "doesn't have one endorsement from one senator."

Search me: "In Iowa, we expect a close race for both parties. Our models predict a win for Donald Trump (39.8% of the votes) over Ted Cruz (30.5%) for the GOP nomination, with Marco Rubio a distant third place (12.9% of the votes). On the Democratic side, we predict a tough battle for Hillary Clinton. Our models calculate that she will beat Bernie Sanders by a small margin (50.1% of the votes for Clinton vs. 46.8% for Sanders)," according to the search engine Bing and their Political Index, which is based on their machine-learning models.

It's all about turnout: "If you think the Iowa caucus electorate is going to be a bit over 120,000 people and have the composition that it typically does, then Cruz will likely win," said University of San Francisco professor Ken Goldstein, according to Bloomberg Politics. "If you think that both the size and shape of GOP caucus participants is likely to be larger and different, then Trump will likely win." Bernie Sanders said voter turnout will determine his fate, as well.

Weather: A blizzard is expected to sweep across Iowa on Monday, and this could keep caucus-goers from participating, but it's not yet clear how early the storm will begin, according to AccuWeather. Drivers who wish to play it safe may skip the caucuses altogether. High turnout appears to benefit Sanders and Trump, while Clinton and Cruz would seem to benefit from lower numbers.

What happens next

On Tuesday, candidates will turn their attention to New Hampshire – indeed, Trump, Kasich and Christie have already moved on to New Hampshire to refocus their efforts – where the next early state voting occurs Feb. 9. It's hard to imagine the field will be as large as Iowa if multiple candidates find themselves in the two percent or lower category.