Washington, DC - The first of several United States Democratic debates will take place on Wednesday and Thursday in Miami, Florida.
Although most candidates have been on the campaign trail for months, the back-to-back nights of debate will be the first chance for some to introduce themselves to millions of voters as they seek to defeat President Donald Trump in 2020.
Immigration, US foreign policy, the economy, healthcare and climate change will likely be hot topics on the debate stage.
As 20 candidates prepare, here's what you should know:
1. When and where will the debate take place?
Because the field of candidates is so large, the Democratic National Committee (DNC) and NBC, who is hosting the first debate in Miami, Florida, split the first debate into two nights: Wednesday and Thursday.
Each night will host 10 candidates.
The debates will last for two hours, beginning at 9pm local time (01:00 GMT). It will air on NBC, MSNBC and Telemundo.
2. Who are the candidates?
Although there are officially 24 candidates (so far), only 20 will be featured during the debate. That is because the other four did not meet the requirements to take the stage.
On Wednesday, Senators Cory Booker, Amy Klobuchar and Elizabeth Warren, Representatives Tulsi Gabbard and Tim Ryan, Washington Governor Jay Inslee, New York City Mayor Bill de Blasio, former Representatives Beto O'Rourke and John Delaney and former Secretary of Housing and Urban Development Julian Castro will take the stage.
On Thursday, Senators Michael Bennet, Kirsten Gillibrand, Kamala Harris and Bernie Sanders, former Vice President Joe Biden, Representative Eric Swalwell, Mayor of South Bend, Indiana, Pete Buttigieg, former Governor of Colorado John Hickenlooper, entrepreneur Marianne Williamson and startup investor Andrew Yang will go head-to-head.
3. Which candidates won't be on stage at all?
Four candidates - Montana Governor Steve Bullock, Representative Seth Moulton, Miramar, Florida, Mayor Wayne Messam and former US Senator Mike Gravel - failed to meet the minimum requirements to get on stage.
Candidates had to poll at one percent in more than three separate polls from a DNC-approved list, or raise money from at least 65,000 unique donors.
4. How does it work?
Each candidate will have 60 seconds to answer questions and will be given 30 seconds for follow-ups.
There will be no opening statements, but each candidate will get one minute for a closing argument.
There are five moderators (split up over the two hours). They include NBC News's Lester Holt, NBC Today show's Savannah Guthrie, Telemundo's Jose Diaz-Balart, Meet the Press's Chuck Todd and MSNBC's Rachel Maddow.
5. What to watch for on night one
Early debates, especially those with such a large field, generally feature fewer outright attacks on opponents and focus more on appealing to voters by highlighting individual platforms and possible points of divergence. But do not be surprised if those participants who have nothing to lose and everything to gain come out swinging.
On Wednesday, Elizabeth Warren, who is the leader of the polls among that night's candidates, will not face Bernie Sanders, with whom she is competing for progressive votes, or Joe Biden, with whom she has the biggest disagreements. Analysts say Warren will be tested as she seeks to make concise arguments on her policy proposals, including Medicare for All, student debt relief or climate change plans.
Also on Wednesday, viewers will see Beto O'Rourke, who made himself a household name during the 2018 midterm elections, running in a surprisingly tight race against incumbent Republican Texas Senator Ted Cruz. During that race, many took notice of O'Rourke's ability to energise voters, something all Democrats are hoping to do as the 2020 race starts a new phase with the debate.
Amy Klobuchar will also be one to watch. Earlier this month, she laid out plans for her first 100 days in office if she gets elected. This included raising the minimum wage for federal contractors, putting the US back in the Paris climate agreement and restoring the Clean Power Plan. Her list included 137 points but did not go into much detail.
Another prominent candidate on Wednesday's stage will be Cory Booker. NBC, citing Booker's campaign, reported that the candidate will focus on telling voters his motivations and the issues he cares about.
The lesser-known candidates, including Julian Castro, Jay Inslee, Bill de Blasio, Tim Ryan and John Delaney, will likely try to create moments that are memorable to voters.
"The most important thing for this debate is making sure broadly he can talk about his experience," Sawyer Hackett, Castro's spokesman, told NBC News. "These are a lot of voters who have not heard from him before."
Of course, do not be surprised if there is quite a bit of Trump-bashing from all the candidates.
6. What are the top issues for voters?
A recent Morning Consult/Politico poll showed Democratic voters want to hear from candidates about their plans for climate change, gun policy and recent abortion legislation.
Other issues voters said they cared about going into the debate included Medicare for All implementation, immigration, education reform and relations with Iran.
7. When is the next debate?
The next series of debates will take place July 30-31. They will be hosted by CNN in Detroit, Michigan.
8. What will Trump be doing during the debate?
Trump will be en route to Japan for the G-20 summit on night one of the debate.
He told Fox Business Network on Wednesday morning that the debate "just seems very boring, but I'm going to watch it because I have to".
