As we get ever closer to the Iowa caucuses, you’re probably going to hear a lot more about whether candidates are on track to meet the 15 percent threshold to qualify for pledged delegates. That threshold matters even in states like Iowa, where there are actually relatively few delegates at stake. And that’s because if a candidate doesn’t hit that threshold — either statewide or at the congressional district level — they will not win any national convention delegates, making a path to the nomination pretty much impossible.

So say we apply that 15 percent threshold to the current national polls. Within the crowded field, only former Vice President Joe Biden and Sens. Bernie Sanders and Elizabeth Warren are polling above that threshold. (Hypothetically, someone like South Bend, Indiana, Mayor Pete Buttigieg could break into that group, especially given his standing in Iowa polls.) A group of four candidates consistently clustered around or above the 15 percent threshold could complicate the race for delegates. But is there any real history of that sort of logjam in Democratic presidential nomination politics?

The short answer is: No. The current 15 percent threshold has been in effect since the 1992 Democratic primary, and since then there has never been a primary or caucus in which four candidates have earned more than 15 percent of the vote state- or territory-wide. But there have been several instances in which three candidates have surpassed that threshold in a single contest, as you can see in the table below.

It’s rare for three candidates to hit 15 percent statewide Results of Democratic presidential primaries and caucuses with at least three competitive candidates, 1992-2016, relative to state- and territory-wide results Year Number of candidates Candidates who won ≥15% of the vote in any contest Contests with 3 candidates who won ≥15% of the vote 1992 5 5 12 2004 9 7 6 2008 8 3 3 2016 3 2 0 Primaries that included an incumbent president or less than three candidates were not included. Candidates who actively contested at least one primary outside their home state were considered competitive. All cycles include 56 primaries or caucuses (50 states plus the District of Columbia and five territories), except for 2016, which added the Northern Mariana Islands to bring the total contests up to 57. Sources: CQ Weekly Report, the green papers, William G. Mayer’s “In Pursuit of the White House”

But even if you applied the 15 percent threshold to cycles before 1992, the picture does not change significantly. Earlier cycles featured contests where four or more candidates got more than 15 percent of the vote, but it was still the exception, not the norm. Between 1972 and 1988, there were only five individual contests where four candidates managed to earn more than 15 percent of the vote state- or territory-wide — less than 2 percent of all contests across those five cycles.

So while much has been made of this idea that the 15 percent threshold could make the primaries particularly messy — technically, as many as six candidates could earn 15 percent of the vote in a given contest, but that’s never happened statewide in the modern presidential primary era. Still, focusing on the results from previous Democratic contests can only take us so far. Yes, there have been past cycles with large candidate fields, but arguably none occurred under conditions comparable to today’s party rules and partisan environment. If we want a better comparison for how the 15 percent threshold might play out, we can turn to the 2016 Republican presidential nomination race — another historically large field.

Republicans don’t impose a 15 percent threshold for allocating delegates in their primary — instead, the Republican National Committee sets a ceiling of 20 percent, and states that proportionally allocate delegates have the latitude to set a lower qualifying threshold — but if they did, the overall outcome would resemble that of the Democrats. No primaries or caucuses had more than three candidates break 15 percent statewide.

But the number of contests where three candidates cleared the 15 percent threshold statewide did last for quite a while in the 2016 GOP primary. In total, 25 out of 57 contests saw three candidates — some combination of Sens. Ted Cruz and Marco Rubio, then-Ohio Gov. John Kasich and Donald Trump — clear the 15 percent threshold statewide. And while most of these contests happened during February and the first half of March, there were some primaries later in the year where this was the case, too. Take the Maryland Republican primary in late April. Cruz, Kasich and Trump all cleared the 15 percent threshold, meaning they would have each gotten some delegates.

This has important implications for Democrats in 2020, though, because if Republicans followed Democrats’ delegate allocation rules, both Cruz and Kasich would have had opportunities to win (or win more) delegates at both the state and congressional district level. Remember, it’s not just statewide delegates at stake in the Democratic primary. Three-quarters of all delegates are awarded based on the results in each individual congressional district.

So let’s look at congressional districts in the 2016 GOP nomination race where three or more candidates cleared that 15 percent threshold. There were a greater number of examples — in total, 119 of 257 relevant congressional districts (or nearly half) saw three candidates break the 15 percent barrier — but it wasn’t like there was a sudden logjam with multiple candidates clearing this threshold. Only in one district did four Republicans receive more than 15 percent of the vote (the 3rd district in Kansas). And again, most of this happened in contests that occurred during the first half of March 2016. But there were a handful of districts where three candidates won 15 percent of the vote in contests that fell in mid- to late April, like Connecticut and New York.

And while that’s not a distinct departure from the statewide results described above, it’s not insignificant either. Depending on how frontloaded a primary calendar is, late April tends to be around the point where enough delegates have been allocated that the presumptive nominee is, if not already clear, coming into sharper focus. So if three candidates are still cresting above the 15 percent threshold by the six-contest “Acela primary” in late April, when more than 75 percent of delegates will have been awarded, that could wreak havoc on the 2020 Democratic nomination process.

But of course, much of this depends on how wide the margin is by which the candidates clear that threshold. If, say, only one candidate is getting a supermajority while the others struggle to hit 15 percent, then the fact that three candidates are above the threshold matters very little — see Trump in 2016. But if three candidates are tightly bunched at 40, 30 and 20 percent, it potentially becomes much more problematic. This is especially true if that clustering happens early and often, especially on delegate-rich days like Super Tuesday, which is scheduled for March 3 this year and is the first series of contests after the four early states.

But here’s why I think a logjam situation is unlikely: How the threshold is applied tends to already have a built-in winnowing effect on the candidates. Yes, there is a proportional allocation of delegates, but that only applies to candidates who win 15 percent of the vote. And that qualifying threshold is not applied just once, but three different times. A candidate must meet that threshold at the statewide level twice, once for at-large delegates and once for party leader and elected official (PLEO) delegates. A candidate must also win 15 percent of the vote in a given congressional district (or other subdivision) to lay claim to any district-level delegates. In other words, a candidate who surpasses 15 percent of the statewide vote by running up margins in a few concentrated areas will not earn as many delegates as a candidate who hits the 15 percent statewide threshold by earning at least 15 percent of the vote across districts. A candidate must build a coalition of support more uniformly across a state — and the country — in order to win delegates. It’s more than just peeling off a delegate or two here and there.

Over the summer, a national reporter asked me what impact it would have on the race if a candidate like Rep. Eric Swalwell (when he was still in the race) managed to pull enough support in his home district to clear the 15 percent threshold. My answer: Not much. If Swalwell received 15 percent of the vote in his Northern California district, that would net him one delegate — not enough to do a whole lot of damage.

So no, it’s not likely that more than three candidates surpass the 15 percent threshold statewide in any 2020 primary or caucus: The bar is just too high.

Ultimately, the 15 percent threshold is actually another way in which the primary field is winnowed. Just look back to when the current 15 percent threshold went into effect in 1992. Sure, there were 12 contests in that cycle where three candidates hit more than 15 percent statewide, but no cycle has come even remotely close to topping that since. In fact, since 1992 there hasn’t been a single cycle where three or more candidates have hit 15 percent statewide in more than a half-dozen contests. That is at least some evidence that the threshold has worked in winnowing the field, and there’s reason to believe it will work again here in 2020. If previous nomination contests are any guide, candidates drop out when it gets too difficult to accrue more — or any — delegates. And voters move on, prioritizing those candidates who can easily clear that threshold.