Donald Trump has dominated the GOP presidential race for seven months. Nothing — not his many offensive comments, not his mediocre debate performances, and not the once-feared GOP establishment — has been able to stop his rise.

But on February 1, all that could change when Trump faces by far his biggest challenge yet: the Iowa caucuses.

The results in Iowa — the first time a state's actual voters weigh in in the presidential nomination contest — can make the national contest turn on a dime. Barack Obama won Iowa in 2008, and he suddenly shot up to become competitive with Hillary Clinton in national polls. John Kerry came out of nowhere to win Iowa in 2004, and the presumed leader, Howard Dean, collapsed with astonishing speed.

And Trump could be vulnerable in Iowa. He has taken the lead in recent polls, but there have been anecdotal reports suggesting that Trump's ground game — crucial in the low-turnout caucuses — is laughably inferior to Ted Cruz's. So in the first contest that really counts, Trump could end up a loser. Yet if he manages to pull off a win — watch out.

But let's step back for a minute, and ask: Why do the quirky Iowa caucuses have this tremendous impact on the race, anyway?

"What is the difference between first place and third place in Iowa going to be, 4,000 votes? It's like a student body election."

The state is small. Its population is overwhelmingly white. Turnout for the caucuses is absurdly low. Democrats don't even get a secret ballot. And vanishingly few of the delegates who will actually determine each party's nominee at the national conventions will be from Iowa. So why do we care so much about who wins?

As I'll explain, Iowa became super important because we — the media, party insiders, activists, the candidates themselves, and even voters to an extent — gradually decided to make it so important. These key players think the caucus results reveal a great deal about which candidates can win elections elsewhere, and the contest for Iowa isn't really a contest for delegates — it's a contest to look good in their eyes.

But does Iowa's prominence make sense? Or could the obsession with its results from the media and insiders alike be a tremendous overreaction, bordering on a bizarre mass delusion — one that could end up distorting who gets nominated for president?

"What is the difference between first place and third place in Iowa going to be, 4,000 votes? It's like a student body election," says Stuart Stevens, who was Mitt Romney's chief strategist in 2012.

"You have to respect the absurdity of it," he continues. "Or it'll drive you crazy."

1) What are the Iowa caucuses?

The Iowa caucuses are the first time actual voters all across any US state get up and go say who they want to be president.

And these voters do literally have to "get up and go" — to an in-person event, held at a specific time in the evening, at one of 1,681 precincts across the state. There's no absentee voting, so if you're bedridden or out of the state, you've historically been out of luck.

(However, this year, for the first time, both parties are letting out-of-state members of the military participate by web, and Democrats are making some allowances for other Iowans who might have trouble showing up.)

The caucuses are administered separately by each major party, and Republicans and Democrats have quite different rules. This year, the GOP contest is simple: After some opening rigmarole at their caucus sites, an ordinary secret ballot vote on presidential candidates will be conducted, and the totals will be tallied statewide.

"It's kind of like a carnival, where the candidates' supporters say, 'Come over to us!'"

The Democratic caucuses are far more complicated — they're rowdy, hours-long public affairs, with back-and-forth debate among attendees who have to go physically stand with other supporters of their preferred candidate. "It's kind of like a carnival, where the candidates' supporters say, 'Come over to us, to our group!'" says Drake University political scientist Dennis Goldford.

There's no secret ballot, and if a Democratic candidate doesn't get enough supporters in a precinct (15 percent of attendees), he or she is eliminated, reality show style. Here's a video showing how one precinct's caucus went down in 2008:

2) Why should I care who wins the Iowa caucuses?

Like it or not, the Iowa results appear to be hugely important in determining who the major parties’ presidential nominees will be — particularly when considered alongside the impact of fellow early state New Hampshire. "It’s not remotely a national primary. These national polls mean nothing. The nation isn't voting," says Stevens. Instead, it's Iowans who get the first say.

Every winner of a competitive major party presidential nomination contest since 1980 except one started off by winning the Iowa caucuses, the New Hampshire primary, or both.

Both of our most recent presidents — Barack Obama and George W. Bush — kicked off their primary season by winning Iowa (and each survived a subsequent loss in New Hampshire).

And, importantly, even if the Iowa victor doesn’t end up winning the nomination in the end, the state’s results can dramatically shake up the presidential contest — knocking some candidates out of the race entirely, while elevating others to top-tier status in the eyes of political elites and future voters.

"You think about the number of people who participate" — usually a little over 100,000 people per party, meaning around 20 percent of eligible caucus-goers — "and Iowa has just an amazing, outsize impact on the country," says Democratic pollster Stan Greenberg.

3) But why, exactly, does this small-time contest affect the larger race so much?

Like you and I, the political world is obsessed with the question of who can actually win in each presidential nomination race. And a large part of that world has come to believe that the caucus outcomes help shed some important light on that question. (Remember, before Iowa, assessments of who can win are mainly based on polls — and polls, of course, can be wrong.)

"Iowa has just an amazing, outsize impact on the country"

It's pretty weird: Essentially, the Iowa caucuses are important because the media, the candidates, and the political world more broadly all treat their results as greatly important in determining who can win. And this plays out in several interacting ways:

The media hypes up the Iowa results, branding candidates as winners and losers based on how they performed there. So the winners get tons of excited coverage, but the losers become afterthoughts. And, particularly in multi-candidate fields, winning media coverage is hugely important. Donors and activists, too, look at the Iowa results to judge whether the candidates they’re supporting are still viable. A poor Iowa performance will likely mean fewer campaign donations and endorsements, which make it more difficult for a candidate to stay in the race. Voters in other states — especially those trying to make sense of complex, multi-candidate fields — can take the Iowa results (and the media coverage of those results) as cues about which contenders can actually win. "There’s no better evidence that you can win than having won," says longtime Democratic pollster Mark Mellman. Accordingly, poll results in other states can change incredibly quickly after the Iowa results sink in. "Up until the caucus, across the country people are only paying attention on the margins," says John Norris, who's organized for several Democratic candidates. The candidates naturally take all this into account, and so many of them invest huge amounts of time and money to try to do well in Iowa. And when the results come in, candidates who do poorly often take the hint and quit the race (spurred by donors who will no longer fund their campaigns, media outlets who no longer cover them, and subsequent polls showing they’re performing poorly elsewhere). This shrinking of the field is a process known as winnowing. And all of these amplify each other: This behavior from candidates further assures the media that the caucus results are really important, which justifies even more coverage of Iowa. "It’s a symbiotic relationship," says Goldford. "So long as the candidates think the caucuses are important, the press will think the caucuses are important. And vice versa."

All of these dynamics, it should be noted, also apply to New Hampshire (and, to a decreasing degree, to other states as the process continues). The media, the candidates, political elites, and to a certain extent voters elsewhere all act on the signals they believe Iowa and New Hampshire are sending them. And that's how these early state contests dramatically reshape the nomination landscape long before the vast majority of the American people get to weigh in.

4) That's pretty abstract. Could you give me some examples about how Iowa has shaken up past contests?

The earliest case in which Iowa changed everything was little-known former Georgia Gov. Jimmy Carter's victory in the 1976 Democratic caucuses. This was only the second time Iowa went first, and Carter calculated that if he won there, he'd get so much media coverage that he'd be catapulted from obscurity to national fame. So he essentially camped out in Iowa for a year, and his strategy worked like a charm when he won.

Carter's subsequent media-driven poll surge helped him narrowly carry New Hampshire and then 11 of the next 12 contests, followed by the nomination and the White House. "Jimmy Carter would say he would never have become president without the Iowa caucuses," says Jerry Crawford, a longtime Iowa Democratic organizer now working for the Clinton campaign.

Iowa convinced people "that Obama was more than just a media phenomenon"

Barack Obama, too, relied on Iowa for his first victory for his campaign against Hillary Clinton in 2008. On the day of the caucuses, he trailed Hillary Clinton by more than 20 points in national polls. But days after he won there, he shot up to within 5 points of her.

"The results of Iowa were validating for us," says Larry Grisolano, who consulted for Obama's campaign that year. "People became convinced that Obama was more than just a media phenomenon — and that he was a candidate who could attract votes."

Obama's win there made him surge to within striking distance of Clinton in national polls, and far above her in another important early contest, South Carolina. "Iowa's peculiarities played to his strengths," Grisolano adds. "I don’t know how it would’ve turned out if we started in a place that was more advertising-centric."

Even when the Iowa winner doesn't end up winning the nomination (as with Mike Huckabee and Rick Santorum, the two most recent GOP winners), the caucus results can shake up the race by elevating them, rather than other candidates, to prominence in the contest.

"The caucuses are about who exceeds expectations and who fails to. And who sets expectations? You and I do."

But it's important to understand that not every candidate is affected equally by the caucuses. Iowa matters primarily because of how it changes the perceptions of the political world. And candidates are, in large part, judged by whether their caucus performance meets the expectations of the media and political elites.

For instance, in the 2008 GOP caucuses, Mitt Romney came in second and John McCain came in fourth. Yet Romney was portrayed as a big loser, since he had been campaigning hard in Iowa and had once seemed the favorite to win. McCain, meanwhile, hadn't really been trying to win Iowa and was focusing instead on doing well in New Hampshire, so his fourth-place finish wasn't interpreted as a stunning setback for him.

"Every candidate in Iowa has the same opponent, and that opponent’s name is 'expected,'" says Goldford. "The caucuses are about who exceeds expectations and who fails to. And who sets expectations? You and I do."

5) This is a bizarre way to pick a president. Why has Iowa been granted so much power?

Essentially, Iowa moved its caucuses to the front of the line at the perfect moment. It happened back in 1972, just while the Democratic Party was overhauling its nomination process to give actual voters, not just party bosses, more of a say. That's how the presidential nomination system we know today — the months-long sequence of staggered primaries and caucuses in every state and territory — came about. (Republicans adopted very similar reforms soon afterward.)

But for 1972 — the first nomination contest under the reformed system — Iowa Democrats slated their usual caucuses for the unusually early date of January 24. People offer various different explanations for why they did so: a deliberate effort to help a favorite son who was considering running for president, an arcane party rules change that required that 30 days pass between various state and local events, or even that a lack of available hotel rooms in Des Moines that summer necessitated an earlier state convention date (which then necessitated an earlier caucus date).

Whatever the reason, the Iowa Democratic caucuses moved ahead of the New Hampshire primary, which had traditionally been the nation's first.

"People in the political community concluded, 'What happened out there told us something'"

At first, few people outside Iowa noticed or cared, and the 1972 caucus results got little attention nationally. But in retrospect, after George McGovern shockingly won the Democratic nomination, insiders second-guessing about why they failed to predict his rise concluded that they should have paid more attention when he finished a surprisingly strong second in Iowa.

"People in the political community concluded, 'What happened out there told us something. It told us about a weak frontrunner. It told us about the energy of the antiwar movement," says David Yepsen, a former political reporter for the Des Moines Register.

Savvy Iowans of both parties worked hard to promote this idea that Iowa was an early bellwether. Democrats arranged the event so top-line "results" could be easily reported to the national press, and Republicans moved their caucuses to the same day to create a unified event that would get lots of media buzz. As Tom Whitney, then state Democratic chair, later told Iowa Public Television:

"Basically after the ‘74 elections, we organized a very, very significant kind of effort to convince first the candidates that they ought to be in Iowa because the national press was going to be here, and then to convince the national press that they should be in Iowa because the candidates were going to be here."

So Carter's victories in Iowa and the general election weren't just great for him — they ended up being great for Iowa, which could now claim to be a kingmaker. Future candidates in both parties spent more time and money there, and the national press started regularly covering the results as a major event. Party insiders and voters in other early states began taking Iowa's results more and more seriously, too.

Ever since, the state parties have tenaciously and successfully fought to keep their caucuses first, helped by the new "precedent" they had set, as Brookings fellow Elaine Kamarck chronicles in her book Primary Politics.

6) And everyone is just okay with giving Iowa so much of a say?

Not at all! Many critics, including Vox's Dylan Matthews, argue that Iowa's population is unrepresentative of the country as a whole — the state is much more white and more rural, and has fewer foreign-born people.

Others criticize the caucus setup itself: The events take a long time, they're scheduled at a specific time in the evening, and there's been no absentee voting in the past, all of which depresses turnout and could make it even more unrepresentative. (Four out of five registered party members in Iowa and the vast majority of independent voters there usually don't show up.)

"I think [Iowa] distorts the process in a good way," says an operative in the state

Furthermore, Democrats don't even get a secret ballot, which means social pressure could skew their results. On the GOP side, turnout has recently been dominated by evangelical activists, many of whom have opted for candidates that lack national appeal, like Huckabee and Santorum.

And presidential candidates of both parties have long felt compelled to voice fealty to powerful interest groups in the state, like Big Corn (though Peverill Squire convincingly argues that pro-corn policies are mainly driven by Congress, not the White House).

Finally, it seems just plain unfair to a lot of people in other states that Iowa gets such power.

Caucus defenders respond by saying that Iowa does skew the results — positively. "I think it distorts the process in a good way," says Crawford, the Hillary Clinton organizer. That's because Iowa's a state where retail campaigning and one-on-one interactions with voters, rather than simply big money and ad buys, matter. Its voters have shown that they don't just follow the prevailing national winds — they're more willing to give little-known and poorly funded challengers a chance, which helps ensure a more democratic contest overall. "Iowa's a level playing ground," says Iowa GOP operative Eric Woolson. "And Iowa has an electorate that pays attention to what's going on."

In any case, every attempt to supplant Iowa has failed, because neither national party can agree on who else should be first in line, or on an alternative way to do things entirely. And states that have tried to "jump the line" — like Louisiana in 1996 — have had their contests boycotted (at Iowa pols' behest) and deemed meaningless by national elites and the press.

Eventually, the national parties accepted that Iowa and New Hampshire were hell-bent on going first and second — and that the vast majority of other states didn't care all that much. So the parties began harshly penalizing other states that tried to move their own nomination contests too early. Accordingly, nobody even bothered to try to leapfrog Iowa this time around.

7) Okay, so we're stuck with Iowa going first for now. Tell me about how it'll affect this year's race.

Once again, it's the lessons the political world takes away from the caucuses that are really important — not how the delegates end up allotted. Everyone is anxious to see how the actual Iowa results measure up to their expectations, to help them better understand who can actually win. And they'll be looking for a few major things.

In the GOP contest, everyone is anxiously awaiting the answer to one key question: "Can Donald Trump get people to actually vote for him?" Because despite Trump's months-long lead in national polls, there's still a great deal of skepticism from elites about him: Perhaps polls overstate his support, perhaps his campaign doesn't have a good ground game, perhaps his supporters who aren't regular GOP primary or caucus voters won't bother to show up, or perhaps the electorate will flock to a more seemingly electable candidate at the last minute.

If Trump wins Iowa, prepare for a media frenzy like you've never seen before

Since caucus turnout is difficult for pollsters to model and since Ted Cruz is perceived as having a better organization than Trump, much of the political world has long expected Trump to finish second, behind Cruz. Yet Trump has taken the lead in all the most recent polls — which has had the perverse effect of raising expectations for him. Now, a second place finish would be viewed as a disappointment for him. And if he comes in third or worse, he'll be portrayed as a loser who went down to a pathetic defeat. But if he does manage to actually win the caucuses, he'll debunk much of that skepticism mentioned above, prove he won't be vanishing from the contest anytime soon — and unleash a media frenzy like you've never seen before.

The Iowa results will have big implications for other GOP candidates too. Since Ted Cruz led polls there until recently, a loss there would be perceived as a serious blow to his candidacy. Marco Rubio, meanwhile, is currently polling in third place, so that's where people expect him to end up. If Rubio manages to surprise people by placing second or even first, he'll get a huge amount of positive buzz going into New Hampshire. But if he somehow falls further behind — especially if another establishment-friendly candidate like Jeb Bush or Chris Christie passes him — whispered doubts about his campaign's competence will be vindicated, and whoever beats him will have the "momentum" of media coverage and buzz among elites in the week before the Granite State contest. And if some other candidate entirely manages to surge late in Iowa (as Rick Santorum did in 2012), expect him or her to be a major player in the next contests, too.

Meanwhile, on the Democratic side, Bernie Sanders has suddenly surged in Iowa polls after a full year of trailing Clinton. Since he's long been ahead in New Hampshire, he's now positioned to seriously compete in both early states. But with this comes raised expectations. If Clinton wins both contests outright, Sanders's movement could well fizzle out, and she could wrap up the nomination quickly. If Sanders wins either, though, or even comes very close in Iowa, expect a pitched battle between the two that will last quite some time. (And unless Martin O'Malley vastly exceeds his current low single-digit percent support in Iowa, expect him to drop out soon afterward.)

The nightmare scenario for Clinton at this point — which is not all that implausible — is that Sanders wins both Iowa and New Hampshire. If that happens, political elites and the press will mercilessly mock and second-guess the Clinton campaign for weeks. Yet insiders also understand that both states are heavily white and not representative of the more diverse Democratic electorate overall. So the big question is whether the positive coverage Sanders gets will improve his performance among nonwhite Democrats who have seemed uninterested in his candidacy so far — and that will be put to the test in the next contest, South Carolina.

"It's a goofy way to do it, I agree. But absent a clear alternative..."

If you feel like you needed a decoder ring to make sense of all that, you're not alone. No one sat down and designed our bizarre presidential nomination system — indeed, even Iowans admit that no one would ever sit down and design this exact system from scratch. "It's a goofy way to do it, I agree," says Yepsen. "But absent a clear alternative the process continues." Candidates keep investing their time and money, the media keeps giving saturation coverage to the results, and political elites keep on believing that Iowa matters — so Iowa just keeps on mattering.

This article was originally published on January 25, 2016. It has been updated with the latest expectations for how the candidates will perform in the caucuses.