Former vice president Joe Biden speaks in Washington on April 5. (Manuel Balce Ceneta/AP)

Donald Trump’s path to victory in the 2016 Republican primary was clearer than it seemed at the time. While it was hard to imagine that a candidate once seen negatively even by Republicans would end up beating a crowded field of more than a dozen experienced politicians, Trump benefited by building a solid core of support soon after his campaign launched. It was largely a function of his willingness to echo far-right rhetoric on immigration, rhetoric familiar to consumers of conservative media like himself.

With about a third of the party behind Trump by the time the primaries started, no one candidate coalesced enough of the rest of the electorate soon enough to offer him a real challenge. He got his delegates, the nomination and the White House.

The 2020 Democratic field is shaping up to be even more sprawling, possibly providing a similarly smooth path for candidates with a strong core base of support. Depending on how you define major candidates, there are already well over a dozen candidates with a feasible shot at winning a significant number of delegates.

Or they would be, if the party’s delegate rules weren’t so weighted to front-running candidates. To explain, let’s mirror the party and start in Iowa.

As the primaries approach, you’ll want to bookmark two sites, Frontloading HQ and the Green Papers. Frontloading tracks changes in and data about the primaries; Green Papers is an even more nerdy look at the delegate-tallying rules and how they work. For example, here’s how Green Papers explains how the Iowa caucuses work:

“At each caucus, each presidential contender who fails to get at least 15 percent support among the participants in the initial balloting after a period of discussion will be considered ‘non-viable’ and all supporters of such 'non-viable’ presidential contenders will then be required to join in the support of presidential contenders who have remained ‘viable’. To determine the viability of a presidential contender, multiply the number of eligible caucus attendees by the percentages below and round to the nearest whole number. This is the minimum number of delegates needed for the contender to remain viable.”

It sounds complex, but the main point is fairly simple. To get any delegates at a caucus, a candidate needs to get 15 percent of the support in the room. So if former vice president Joe Biden gets 27 percent of the vote at a caucus, Sen. Bernie Sanders (I-Vt.) gets 16 percent and South Bend, Ind., Mayor Pete Buttigieg gets 9 percent (as a recent Monmouth University poll has them statewide), Buttigieg would be out of the running. Everyone who supported another candidate, including those Buttigieg backers, would have to pick either Biden or Sanders.

So only Biden or Sanders would get any delegates.

That 15 percent rules carries across primaries. In New Hampshire, where only Biden and Sanders were over 15 percent in a recent St. Anselm University poll, only Biden and Sanders would get any delegates. In Nevada’s caucuses and South Carolina’s primary, recent polling again has only Biden and Sanders over 15 percent. Obviously that will change over the course of the first few contests as candidates drop out and throw their weight behind other candidates, but if the field still has 10 people in it by the time Super Tuesday rolls around — March 3, 2020 — the same pattern could hold.

If we use current polling in those first four contests and apply the party’s sort-of-weird delegate math, the total number of pledged delegates that would be assigned would look like this:

Candidate Iowa N.H. Nev. S.C. Total
Biden 26 14 19 34 93
Sanders 15 10 17 20 62
Everyone else 0 0 0 0

On March 3, there are a slew of other primaries, including in California, where Quinnipiac University currently has Sen. Kamala D. Harris (D-Calif.) getting 17 percent support. If we assume that Biden, Sanders and Harris all get the same amount of support in the state that is reflected in that poll, here’s how the count would stand after the first four states and California:

Candidate First four Calif. Total
Biden 93 177 270
Sanders 62 123 185
Harris 0 116 116
Everyone else 0 0 0

This is a system that works well for a field of two or three candidates. It works less well for a field of 20 candidates.

It’s possible that Biden and Sanders will fade and the Democratic field will be a mush of seven or eight candidates with about 10 percent support. In that case, things get a bit more fair: The threshold for getting delegates falls to half the highest amount of support a candidate received. So if Biden got the most support in a state at 14 percent, anyone who got at least 7 percent support would be eligible for delegates.

If Biden and Sanders stay some distance from the pack, though — and, you know, if Biden runs — they’re in an enviable position at the moment.

At the moment, Sanders can certainly attest to the fact that front-running Democratic primary candidates can suddenly find themselves in a fight with an unexpected challenger.