Tonight, for­mer Vice Pres­i­dent Joe Biden and Sen­a­tor Bernie Sanders will face each oth­er in the eleventh Demo­c­ra­t­ic pri­ma­ry debate.

The cir­cum­stances sur­round­ing this debate could not be more dramatic.

Since the last debate – back on Feb­ru­ary 25th – the whole dynam­ic of the Demo­c­ra­t­ic pri­ma­ry has been upend­ed. Back in late Feb­ru­ary, Sen­a­tor Sanders was the undis­put­ed front run­ner, hav­ing won the pop­u­lar vote count in Iowa, New Hamp­shire and Neva­da (the first ever can­di­date to do so). He faced six rivals (includ­ing Biden), none of whom appeared to have any viable path to the nomination.

In the days fol­low­ing the debate, how­ev­er, Joe Biden staged a record-shat­ter­ing come­back; a con­vinc­ing vic­to­ry in South Car­oli­na led to a flood of endorse­ments from pow­er­ful par­ty fig­ure­heads, rival can­di­dates drop­ping out en masse, and ulti­mate­ly to a mas­sive suc­cess on Super Tues­day.

Biden’s can­di­da­cy went from a zom­­bie-like fugue to front run­ner almost overnight. Sanders, mean­while, was left reel­ing and uncer­tain of how to proceed.

Bernie Sanders and Joe Biden are the only cred­i­ble 2020 Demo­c­ra­t­ic can­di­dates still seek­ing their par­ty’s pres­i­den­tial nomination.

All of these devel­op­ments have been dwarfed, how­ev­er, by the rapid­ly wors­en­ing glob­al coro­n­avirus pan­dem­ic. Entire coun­tries have gone into lock­down, many states have imple­mented dra­con­ian mea­sures “not seen since the Span­ish flu”, and Don­ald Trump him­self had a health scare.

Con­se­quent­ly, the debate will take on a dif­fer­ent tone and format.

Instead of fac­ing each oth­er in front of a live audi­ence in Ari­zona, Biden and Sanders will debate in a TV stu­dio in Wash­ing­ton D.C. with­out an audi­ence, in order to mit­i­gate the risk of viral infection.

The threat of COVID-19 will undoubt­ed­ly dom­i­nate the debate, much as it has dom­i­nat­ed news head­lines across the world.

Both can­di­dates can poten­tial­ly ben­e­fit. In a bril­liant move, Joe Biden – who has por­trayed his can­di­da­cy as a “return to nor­mal­cy” – made a speech address­ing the cri­sis that came across as pres­i­den­tial, com­pe­tent and persuasive.

The emer­gency mea­sures he sug­gest­ed con­trast­ed strong­ly with the incom­pe­tence of the Trump Administration’s response to the pandemic.

Bernie Sanders, mean­while, has used the glob­al pan­dem­ic to make a more expan­sive argu­ment about the entire U.S. health system.

While going after Trump’s incom­pe­tence, Sanders argued that the U.S. is par­tic­u­lar­ly vul­ner­a­ble to the pan­dem­ic because it lacks uni­ver­sal healthcare.

In light of the ben­e­fits oth­er coun­tries are reap­ing from their uni­ver­sal health­care sys­tems to com­bat the coro­n­avirus, Sanders’ sig­na­ture pol­i­cy of Medicare for All look more and more essen­tial every day that the cri­sis continues.

Since there will only be two can­di­dates on stage on Sun­day, the debate over health­care will be more clear-cut than it has been before. Both Sanders and Biden have robust and well-thought-through poli­cies, and vot­ers watch­ing this debate will be able to direct­ly com­pare them, with­out the dis­tract­ing input of Pete Buttigieg and Amy Klobuchar’s nit-pick­­ing or Eliz­a­beth Warren’s con­fus­ing polit­i­cal “piv­ot­ing” that obscured the issue in pre­vi­ous debates.

Beyond advo­cat­ing for their respec­tive health­care posi­tions, the two can­di­dates have clear – if very dif­fer­ent – objec­tives for this debate.

Bernie Sanders’ can­di­da­cy may be in dire straits, but he is not out of the race. Sanders cur­rent­ly has about 150 few­er del­e­gates than Biden (736 to Biden’s 890) but there is def­i­nite­ly room for him to catch up, since both are far below the num­ber of del­e­gates need­ed to win a major­i­ty at the Demo­c­ra­t­ic Nation­al Con­ven­tion (1,991). Besides, the sep­tu­a­ge­nar­i­an social­ist always thrives as an under­dog – his cam­paign soared after Sanders suf­fered a heart attack on the cam­paign trail!

Sanders is not fin­ished yet, but Sunday’s debate could be his last shot; two days after the debate, the states of Ari­zona, Flori­da, Illi­nois and Ohio hold their pri­maries — or, at least, they are sup­posed to. If Sanders can’t fig­ure out a way to change the dynam­ics of the race by Tues­day, the for­mer Vice Pres­i­dent could rack up a del­e­gate lead from these large states that is all but unassailable.

If Sanders wants to turn the tables on Biden, he needs to shake the for­mer Vice President’s grip on his base of elder­ly and African Amer­i­can voters.

To do that, Sanders needs to make Biden own his past sup­port for cut­ting Social Secu­ri­ty ben­e­fits for the elder­ly and his oppo­si­tion to “bus­ing” pro­grams intend­ed to bring about racial deseg­re­ga­tion in the coun­try’s schools.

Cri­tiques like these have worked before – last sum­mer, Sen­a­tor Kamala Har­ris received a sig­nif­i­cant bounce in pub­lic opin­ion research sur­veys at the expense of Biden after tak­ing on the for­mer Vice Pres­i­dent in the first Demo­c­ra­t­ic debate.

How­ev­er, Har­ris and Sanders have very dif­fer­ent debat­ing styles.

Sanders has fre­quent­ly exas­per­at­ed pro­gres­sives by fail­ing to be suf­fi­cient­ly tough in con­fronta­tions with neolib­er­al Democ­rats such as Biden.

Biden’s main objec­tive is sim­ply to stay the course; all he needs to do is appear pres­i­den­tial, stay calm, and come across as rea­son­ably likable.

Bar­ring any major gaffes, Joe Biden can sim­ply surf to victory.

How­ev­er, Joe Biden is a man who has turned the gaffe into an art form. Over the past year on debate stages, the for­mer Vice Pres­i­dent has said that the solu­tion to domes­tic abuse is to “keep punch­ing,” gone on an epic and baf­fling rant about record play­ers, and even tried to send sup­port­ers to the wrong cam­paign web­site.

Biden is prone to gaffes when under pres­sure – his best debate per­for­mances have come when the spot­light is decid­ed­ly away from him (such as the Bloomberg pile-on a month ago). How­ev­er, there will be nowhere for Biden to hide on Sun­day, and there is no guar­an­tee that he can keep his head if Sanders applies the pres­sure. On the oth­er hand, he only has to wor­ry about debat­ing one opponent.

The stakes in this debate are per­haps high­er than they have ever been for the 2020 race, which should hope­ful­ly make for good view­ing! The debate can be watched on CNN, CNN en Español, CNN Inter­na­tion­al, and Uni­vi­sion begin­ning at 5 PM Pacif­ic Time. It will also be livestreamed on CNN.com.