Written By Priyanka Aribindi

After every Democratic primary contest, reporters and pundits fixate on the same handful of terms: “delegates,” “thresholds,” “brokered conventions.” By now, you get the gist—primaries are contests for delegates, and delegates are the key to winning the nomination. But how does it all actually work? What happens when candidates win delegates, then drop out of the race? And how will one of the two remaining candidates in the race (sorry, Tulsi) become the nominee?

The process is way more complicated than the gist suggests, so let’s start with the basics:

What is a delegate?

A delegate is a person (a real live person!) who will vote to nominate a candidate at the Democratic National Convention, where the party’s nominee will be officially chosen in July. When Democrats vote in their state’s primary, they’re essentially instructing their state’s delegates how to vote at the convention. Kind of like how in presidential elections, we vote to tell our states’ “electors” whom to give the presidency to.

Let’s start with the delegates who carry out the will of the voters, or “pledged delegates,” because they’re the ones we talk about during primaries and caucuses.Pledged delegates tend to be active in Democratic politics: local office-holders, party activists, and/or regular people who were early supporters of specific candidates. Voters and state parties determine which specific individuals serve as pledged delegates and go to the convention to participate in the selection of the nominee.

How many delegates are there?

There are a total of 4,750 delegates. 3,979 of these are “pledged” delegates—the ones that are up for grabs during primaries and caucuses. Of these, 2,591 are pledged at the district-level, and the other 1,388 are pledged at the state-level. The remaining 771 are superdelegates, who only come into play at the party’s national convention. More on those shortly.

States and territories are assigned different numbers of pledged delegates based on a formula that accounts for the number of “electors” the state has in the electoral college (which is just the number of House representatives it has plus its two Senators), how many votes the Democratic nominee received in the state’s past three presidential elections, and the timing of the state’s primary. That means bigger, bluer states send more delegates to the convention than smaller, redder ones.

How do candidates get delegates?

Delegates are awarded proportionally to the candidates based on how many votes they get in each state’s primary contest, but it’s not as simple as getting the same percentage of delegates as popular votes.

There are two kinds of pledged delegates—statewide and district-level. If a candidate receives over 15 percent of the votes across an entire state, that candidate becomes eligible to receive statewide delegates, which get divided proportionately between candidates who clear that threshold. Candidates who don’t clear the 15 percent statewide threshold can still score district-level delegates by receiving over 15 percent of the votes in specific congressional districts.

What happens when someone drops out?

If the candidate in question dropped out before winning any delegates, nothing happens. They move onto the next thing—running for another office, resuming their day job, endorsing another candidate, and maybe even scoring a gig doing commentary on cable news.

If they did win delegates (like Pete Buttigieg, Amy Klobuchar, Mike Bloomberg, and Elizabeth Warren), it’s a different story.

After all the primary contests are over (around June or so), the statewide pledged delegates those candidates won will be proportionally reallocated between the remaining candidates (Biden and Sanders, assuming they take the race to the convention) based on how they performed in those states. Easy.

Here’s the hard part: District-level pledged delegates won by former candidates are not reallocated in the same way. Technically, they’re still pledged during the first round of voting at the Democratic National Convention, but nothing requires them to follow through and actually vote for those candidates. When they get to the convention, they can become free agents and support whomever they want. These delegates could be influenced by the endorsements of the candidates they were originally pledged to—meaning that a district-level delegate originally pledged to Buttigieg may choose to back Biden because that’s who Buttigieg himself endorsed—but nothing requires them to do that.

How does a candidate actually win the Democratic nomination?

The easy way to win the nomination is by receiving the support of a majority of pledged delegates (so 1,991 delegates or more) in the first round of voting at the Democratic National Convention.

But things could get messy. There’s a chance one candidate will arrive at the convention with a plurality, meaning more pledged delegates than any other candidate, but not an absolute majority (over 50 percent of those pledged delegates).

So what happens if no one wins a majority?

Buckle up. This scenario triggers what’s called a “contested convention” (or a “brokered convention”—they mean the same thing).

If after the first round of voting at the convention, no candidate has received 1,991 delegats, the convention enters a second round of voting. If that happens, all the delegates become free agents. That’s also when the 771 superdelegates enter the mix.

Ok, I’ll bite—what’s a superdelegate?

Superdelegates are party insiders who get to support whoever they want as unpledged delegates in the second (and any subsequent) rounds of voting.

They include Democratic senators, governors, House members., DNC members, and “distinguished party leaders” like Barack Obama. Biden and Sanders themselves are both superdelegates, along with several other former Democratic presidential candidates.

Why do superdelegates have such a bad rep?

Superdelegates are current and former party leaders who aren’t selected to serve at the convention by Democratic primary voters, and get to support whomever they want. The whole concept was developed to give party elites a level of control over the process, in case voters picked someone they deemed unfit to be the nominee. It’s not hard to see why that doesn’t exactly seem fair.

In 2016, superdelegates were allowed to participate in the first round of convention voting, and hundreds of them pledged their support to Hillary Clinton before she had won a majority of pledged delegates in the primary. This appeared to ensure that she’d win the nomination regardless of what primary voters decided between her and Bernie Sanders.

Because of this, the party came under immense pressure to change the rules, and the DNC obliged. In 2018, they stripped superdelegates of much of their power by making them ineligible to participate in the first round of voting at the convention.

So what happens if superdelegates enter the mix?

Chaos. That’s not really an exaggeration. Even though superdelegates have much less sway this cycle and have never flouted the will of Democratic primary voters in the past, it would still threaten to divide the party.

To win on the second (or any subsequent) ballots at the convention, a candidate needs to secure a majority of total delegates. Because there would be a total of 4,750 delegates voting (the 3,979 pledged delegates plus the 771 superdelegates), the winner would need the support of over 2,375 pledged and superdelegates.

Since all delegates become free agents at this point, the campaigns would be allowed to fan across the convention, trying to persuade or cajole any undecided delegates to back their candidates. Even if the plurality winner walked away with the nomination after this process, it’s easy to see why it would leave the losing campaign’s supporters with hard feelings.

That… doesn’t sound great. Any reassurance before you end on perhaps the most uncertain note of all time?

Yes, actually! In an interview on March 5, Bernie Sanders told MSNBC’s Rachel Maddow that if Joe Biden entered the Democratic National Convention with the most pledged delegates, but not the outright majority he’d need to secure the nomination, Sanders would support Biden as the nominee. This was not Sanders’ position in 2016, but that was because of the role superdelegates played in the first round of voting at that convention. Because the rules have changed, Sanders has said throughout this primary that whoever wins a plurality of votes during the primary process should be the party’s nominee.

Biden, like several other (now former) candidates, has said that the nominee should be selected through the party’s standard process if no candidate receives a clear majority of pledged delegates.

In other words: Biden has left the door open for a contested convention if he arrives in Milwaukee with fewer delegates than Sanders, but Sanders’s stated position would preclude the chaos of a contested convention.

This piece has been updated for clarity.