Here’s what we know about how the 2020 Democratic convention will work, what candidates need to win in different scenarios, how an intra-party fight over rules following the 2016 election set up where we are today, and more.

How does a candidate win the nomination?

Candidates can secure the Democratic presidential nomination by winning a majority plus one of the pledged delegates up for grabs on the first ballot — that is, 1,991 of the 3,979 delegates awarded for winning votes in caucuses and primaries in the 50 states, the District of Columbia, Puerto Rico and other U.S. territories.

There are three types of pledged delegates: at-large delegates, pledged leaders and elected officials (PLEOs) and district-level delegates. The first two types of delegates — at-large and PLEOs — are awarded proportionally to candidates who get more than 15 percent of the vote (the “viability threshold”) statewide. The district-level delegates are awarded to candidates who clear that 15 percent threshold in designated districts — meaning candidates can be viable in a district in a state even if they aren’t doing well statewide. The districts are usually congressional districts, but some states use other lines to award those delegates.

But what about the superdelegates? Where do they come into this?

Superdelegates, otherwise known as automatic delegates, cannot vote on the first ballot — except as a formality in the event that a candidate is already running away with a pledged delegate majority. This reduction of superdelegates' role was one of the major reforms that came out of the Unity Commission, a collection of Bernie Sanders and Hillary Clinton supporters that came together to redo the Democratic National Committee’s rules after the 2016 election.

There are 771 superdelegates to the national convention who, broadly, fall into three categories: Elected officials, DNC members, and “distinguished party leaders.” If no candidate reaches 1,991 pledged delegates on the first ballot, superdelegates can vote on the second ballot and any subsequent ones after that.

To win on subsequent ballots and secure the nomination, candidates need to get 2,375.5 delegates (some superdelegates have half votes).

Who are the superdelegates?

Elected officials include every Democratic member of Congress (that includes Sanders, who is an independent but caucuses with the Democrats), as well as Democratic governors and the mayor of Washington, D.C.

About two dozen delegates are distinguished party leaders, a category that includes former Democratic presidents, vice presidents (hello, Joe Biden) congressional leaders and party chairs.

The last remaining group is Democratic National Committee members, who constitute the majority of the superdelegates. DNC members include state party chairs and committee members elected by state parties, along with at-large members.

People who fit into more than one of these groups do not get to vote twice. Rep. Debbie Wasserman Schultz (D-Fla.) is both a member of Congress and, as a former DNC chair, a distinguished party leader. But she gets just one vote.

Several of the candidates running for the nomination are superdelegates themselves. Biden, Sanders, Elizabeth Warren, Amy Klobuchar and Tulsi Gabbard are all superdelegates. Mike Bloomberg and Pete Buttigieg are not.

Are delegates legally required to vote for a candidate?

Neither pledged nor automatic delegates are legally required to back any particular candidate, according to national party rules. While that might sound like chaos waiting to happen, the reality is fairly boring and straightforward: The candidates have more control than ever over who their delegates are, and the loyalists who get those positions are likely to take their cues from their candidates.

The DNC’s delegate selection rules say that pledged delegates “shall in all good conscience reflect the sentiments of those who elected them” — a bit of legalese saying they are not legally bound and can vote their consciences. But the candidates have veto power over who can become a pledged delegate for them after they win.

Here’s what the DNC rules say: State parties must allow “presidential candidates, or their authorized representative(s), to review the list of persons who have filed [to be a delegate], and to remove from that list persons not confirmed by the presidential candidate or his/her representative(s) as bona fide supporters of the presidential candidate.”

Presidential candidates who drop out before the convention can choose to “release” their pledged delegates, but it is not something they are required to do. And superdelegates — who, again, cannot affect the outcome of the first-ballot vote — are free to back whomever they like. Their vote is not tied to the results of their home state or anything else other than their personal decisions.

What are the odds of a contested convention happening? Is it too early to say?

It depends on who you ask. The prospect of a contested convention has been raised at some point in just about every cycle where an incumbent is not running, but there hasn’t been a fight on a convention floor in nearly 70 years.

We’re still incredibly early in the nominating process. Forecasters like FiveThirtyEight have projected that, as of right now, the most likely outcome is that no candidate wins a majority of pledged delegates, but their projections are a moving estimate that can change as more states vote — and everything can change quite quickly.

After all the results from Super Tuesday are finalized, about 40 percent of pledged delegates will be allocated. Just two weeks later, on March 17, over 60 percent of delegates will be out the door. And by the end of April, roughly 90 percent of pledged delegates will have been awarded.

Okay, but what about 2016? Superdelegates handed Hillary Clinton the nomination over Sanders, right?

Clinton won the majority of pledged delegates in 2016, as well as the majority of superdelegates. If the 2016 convention rules were the same as the 2020 convention rules, where only pledged delegates were able to vote on that first ballot, Clinton still would have won the nomination.

But the 2016 rules were not the same. Superdelegates could vote on the first ballot in 2016, and an overwhelming number of them supported Clinton.

Sanders’ beef with superdelegates in 2016 was more of a process argument: Clinton’s commanding superdelegate lead was reported widely by the press and included in most delegate trackers. That, they argued, gave Clinton an aura of inevitability that stunted Sanders’ momentum, even as he began to challenge and beat Clinton in actual primary contests, that was hard to overcome.

Sanders tried to recruit superdelegates to flip on Clinton in 2016.

“If we come a little bit short, I still think we’re going to be in a very strong position to argue that — if you look at the progress that Bernie made, if you look at the standing that he has, particularly versus Trump in the polls, if you look at where we started and where we finished,” then-Sanders adviser Tad Devine told POLITICO in 2016. “It’s a very, very strong argument that he would be the best choice to be the nominee. I think we’ve all resolved, ‘why don't we let the voters have their say first’ and our goal is to tie this thing up.”