We’re halfway through the first Democratic presidential debate — the second and final night of the event will take place from 9 to 11 pm ET on Thursday in Miami and will air on NBC, MSNBC, and Telemundo. You can watch it at this YouTube link or through an over-the-top device or subscription streaming service that carries NBC — like Fubo or Sling TV.

The most notable contenders in tonight’s roster will be Joe Biden, Bernie Sanders, Kamala Harris, and Pete Buttigieg. They are four of the five top-polling Democratic candidates overall, with Biden remaining the clear frontrunner, which makes him a potential target.

Another half-dozen candidates who are polling around the 1 percent level — some politicians, but also a pair who have never held elected office — will also be trying to take advantage of this national platform to better stand out in the field.

Really, though, this debate is most noteworthy as the first major test for Biden. The former vice president has led nearly every national and early-state poll so far this year, and he’s currently ahead by 15 percentage points in the RealClearPolitics national poll average. Currently, he’s winning. But he also has some serious weaknesses.

This debate gives Biden an opportunity to set doubts about him to rest — but it’s also a high-pressure setting in which his rivals could make trouble for him, or in which Biden could make trouble for himself.

Where the Democratic race stands before the first debate

Biden is winning — but he’s facing tougher attacks: There are 25 at least somewhat notable Democratic candidates in the race, 20 of whom qualified for the first debate. But there’s just one who is indisputably the man to beat: Joe Biden.

Many Democratic voters perceive Biden as the most “electable” candidate (an assessment that is generally backed up by polls pitting the candidates against President Donald Trump). They may also have fond memories of the Obama administration and view Biden as next in line. Yet certain aspects of Biden’s political persona fit uncomfortably with a changing Democratic Party, and those problems came to the fore last week.

At a recent fundraiser, Biden reminisced about how he used to be able to work productively with segregationist senators (in contrast to today’s lack of “civility”). The comments sparked criticism from several candidates, including Cory Booker, who called on Biden to apologize. Biden also has been much more skeptical of the “class warfare” economic message that candidates like Sens. Bernie Sanders and Elizabeth Warren have embraced — and at the same fundraiser, he told wealthy donors that though “income inequality” needs to be addressed, “nothing will fundamentally change” for them during his presidency.

These are just the latest of many examples in Biden’s career where his mouth has gotten him into some trouble. Separately, there are also questions about Biden’s age: He is 76 and would be 78 years old by Inauguration Day 2021. He’s been effective at debates in the past — but will he be so again?

Sanders, Warren, Harris, and Buttigieg are the rest of the top tier: Beyond Biden, four other candidates have emerged from the pack in polls so far.

Vermont Sen. Bernie Sanders has most often been in second place — and while his support remains significant, his coalition from 2016 has clearly split somewhat in the more crowded field. Sanders continues to have a rather antagonistic relationship with Democratic Party leaders, and his campaign is probably the biggest threat to the party establishment.

has most often been in second place — and while his support remains significant, his coalition from 2016 has clearly split somewhat in the more crowded field. Sanders continues to have a rather antagonistic relationship with Democratic Party leaders, and his campaign is probably the biggest threat to the party establishment. Then there’s Massachusetts Sen. Elizabeth Warren , who was in the Wednesday night debate and won’t be participating tonight. She had a weak start to the campaign but has taken a policy-heavy approach (she “has a plan for that,” the catchphrase goes) and has recently risen to third place. Warren’s rise has been a problem for Sanders, since the two are both on the Democratic Party’s left flank on economic issues.

, who was in the Wednesday night debate and won’t be participating tonight. She had a weak start to the campaign but has taken a policy-heavy approach (she “has a plan for that,” the catchphrase goes) and has recently risen to third place. Warren’s rise has been a problem for Sanders, since the two are both on the Democratic Party’s left flank on economic issues. California Sen. Kamala Harris is a rising star in the national party — she was first elected to the Senate in 2016 after a six-year stint as her state’s attorney general and now hopes to become the first black female president. She remains a top-tier candidate, but she’s had some trouble getting headlines — and currently, she’s not getting all that much support from black voters.

is a rising star in the national party — she was first elected to the Senate in 2016 after a six-year stint as her state’s attorney general and now hopes to become the first black female president. She remains a top-tier candidate, but she’s had some trouble getting headlines — and currently, she’s not getting all that much support from black voters. South Bend, Indiana, Mayor Pete Buttigieg has done the best of any candidate who started off the year unknown. Many national Democrats were impressed with the 37-year-old Harvard-educated gay veteran, and Buttigieg’s polling and fundraising numbers soon reflected that. However, these Buttigieg supporters have so far tended to be overwhelmingly white, and his relationship with the black community in South Bend isn’t great, as the controversy over a recent police shooting in the city has demonstrated.

A whole lot of other candidates are trying their luck: Finally, one thing the first night of the debate has already made unmistakably clear is that there are a lot of Democrats in this race. The combination of Trump looking beatable, Biden not being an overwhelmingly dominant frontrunner, and Trump’s own surprising outsider win has spurred many Democrats to wonder: Why not me? Lenient qualification standards have let nearly all of them get into the first debate, and now they’re all hoping to have some sort of “moment” that will send them into the top tier.

The debate night rosters and dynamics

Knowing that the field of candidates would be enormous, the Democratic National Committee tried to avoid repeating Republicans’ example in 2015, when they featured a primetime debate of the top-polling candidates and an earlier “kids’ table” debate with those polling worse.

So the DNC separated the candidates into groups — those polling at 2 percent or above, and those below that level. They ensured that each group would be split equally between the two nights and then held a random drawing to see which candidates would be on each night.

The candidates who debated on the first night were Warren, Booker, Beto O’Rourke, Julián Castro, Amy Klobuchar, Tulsi Gabbard, Tim Ryan, Jay Inslee, Bill de Blasio, and John Delaney. They’re done until the next debate in July.

So here is the lineup for tonight:

From left, the roster is:

Because of the luck of the draw, this is effectively the marquee night for the debate — with frontrunner Biden, second-place Sanders, and tied-for-fourth-place Harris and Buttigieg all onstage.

And all eyes will be on Biden. He’s certainly no stranger to the format; his first presidential debate was 32 years ago, and he was in several more during his 2007 campaign, as well as general election vice presidential debates in 2008 and 2012. Still, for the clear frontrunner, the pressure will be on, and his rivals will be sure to pounce on any misstep.

Sanders, for instance, will have an opportunity to make the case that his vision for the presidency would be far different — he wants a “political revolution,” whereas Biden emphatically does not. Harris and Buttigieg, too, could argue that new leadership is needed for the party. But it’s not clear just how aggressive these candidates will be in attacking Biden; they could decide it’s a mistake to go too negative this early.

The two Democratic candidates without experience in political office will also be onstage this night. Williamson, an author who has written on spirituality, has recently tried to backtrack from comments she made criticizing vaccines. Meanwhile, Yang will tout his plan for a universal basic income of $1,000 a month. With most of the top-polling contenders as well as Williamson and Yang on this night, it may be more difficult for the other politicians onstage — Gillibrand, Bennet, Hickenlooper, and Swalwell — to stand out.

What comes next

The second Democratic debate, on July 30 and 31, will be a similar two-night affair, with similar qualification rules.

But after that, the DNC has said, it’s raising the bar. Candidates will have to hit 2 percent in at least four polls, and they’ll also have to have 130,000 unique donors. The donor threshold in particular will be challenging for many candidates who currently don’t have national followings. So the third debate could well have a far smaller lineup.

This week, though, almost everyone will get a chance to go onstage and make their case — for a few minutes, at least.