The most unique presidential debate in recent memory took place Sunday night, when former Vice President Joe Biden and U.S. Sen. Bernie Sanders debated each other in a Washington, D.C., studio with no audience.

The debate, hosted by and broadcast on CNN, is believed to be the first one-on-one presidential debate to be held in a studio, with no audience, since 1960. John F. Kennedy and Richard Nixon were the Democratic and Republican nominees, respectively, and were facing each other in the general election.

Biden and Sanders are Democrats battling for their party’s nomination to face President Donald Trump this November.

The debate was being held in the middle of the global coronavirus pandemic. Both CNN and the Democratic National Committee agreed the debate should be hosted without a studio audience.

»MORE: Coronavirus fears cause DNC, CNN to prohibit audience, press room at next debate

Biden and Sanders skipped a handshake, greeting each other instead with an elbow bump, then took their positions at podiums spaced 6 feet apart in keeping with guidance from the Centers for Disease Control and Prevention for limiting the virus’ spread.

The next viral social media moment came less than a minute into the debate, when Biden began his comments with a cough.

Both Biden and Sanders called for increased testing in the U.S. for the rapidly spreading coronavirus and economic relief for Americans suffering as a result of the global pandemic.

“This is bigger than any one of us. This calls for a national rallying for one another," the former vice president said.

Sanders panned Trump's handling of the crisis, urging the president to stop hindering medical professionals by “blabbering with unfactual information that is confusing the American public."

Sanders said if he were president he would make sure no one has to pay for coronavirus testing or treatment. Biden later said he also believes no one should have to pay.

The coronavirus pandemic dominated the start of the debate, reflecting how quickly it has also overtaken almost every aspect of American life. Schools are shut down across the country, travel has been significantly limited and the likely economic consequences have sent financial markets plummeting.

Biden and Sanders both called for increased testing for the virus and economic relief for Americans who will suffer.

The fact the debate was held without a studio audience received mostly positive reviews.

Biden and Sanders face each other Tuesday in four presidential primaries, including the important Florida race as well as Illinois, Ohio and Arizona.

On March 17, 577 delegates are at stake in Florida (219); Illinois (155); Ohio (136); and Arizona (67).