It was the first one-on-one debate of this primary season.

Former Vice President Joe Biden and US Sen. Bernie Sanders faced off Sunday night in the nation's capital, making their case to Democratic voters a couple of days before primaries in Arizona, Florida, Illinois and Ohio.

The two candidates entered the debate under unprecedented circumstances.

The coronavirus pandemic has led to both candidates canceling rallies and staying off the campaign trail in recent days. Sunday's debate was originally supposed to take place in Arizona in front of a live audience. But instead, it took place in CNN's Washington studios with no audience.

The candidates face each other during the debate. Because of the coronavirus pandemic, their podiums are more spread out than usual.
The candidates face each other during the debate. Because of the coronavirus pandemic, their podiums are more spread out than usual.
Sarah Silbiger for CNN
The debate is taking place in CNN's Washington studios. There is no live audience.
The debate is taking place in CNN's Washington studios. There is no live audience.
Sarah Silbiger for CNN
Sanders walks by as Biden talks to the moderators after the debate.
Sanders walks by as Biden talks to the moderators after the debate.
Gabriella Demczuk for CNN
Biden and Sanders' responses to the coronavirus highlighted their unity in opposing President Donald Trump, as both believe he has mishandled this crisis. But they have <a href="index.php?page=&url=https%3A%2F%2Fwww.cnn.com%2F2020%2F03%2F15%2Fpolitics%2Fdemocratic-debate-tonight%2Findex.html" target="_blank">different approaches and philosophies.</a> Biden is pledging competency that leads voters to harken back to how former presidents responded in a time of crisis. Sanders is promising wholesale change.
Biden and Sanders' responses to the coronavirus highlighted their unity in opposing President Donald Trump, as both believe he has mishandled this crisis. But they have different approaches and philosophies. Biden is pledging competency that leads voters to harken back to how former presidents responded in a time of crisis. Sanders is promising wholesale change.
Gabriella Demczuk for CNN
"People are looking for results, not a revolution," Biden said. "They want to deal with the results they need right now."
"People are looking for results, not a revolution," Biden said. "They want to deal with the results they need right now."
Gabriella Demczuk for CNN
Sanders followed up Biden's remarks by saying that it is "not good enough not to be understanding how we got here and where we want to go into the future." <a href="index.php?page=&url=https%3A%2F%2Fwww.cnn.com%2Fpolitics%2Flive-news%2F2020-democratic-debate-live-updates%2Fh_0afea0722aa83135db23010fda6bf31c" target="_blank">The back-and-forth</a> highlighted the key differences between the two candidates.
Sanders followed up Biden's remarks by saying that it is "not good enough not to be understanding how we got here and where we want to go into the future." The back-and-forth highlighted the key differences between the two candidates.
Sarah Silbiger for CNN
A look inside the control room at CNN's studios in Washington.
A look inside the control room at CNN's studios in Washington.
Gabriella Demczuk for CNN
Biden looks at a video screen as a taped question is asked.
Biden looks at a video screen as a taped question is asked.
Gabriella Demczuk for CNN
The podiums are 6 feet apart, per recommendations from the Centers for Disease Control and Prevention.
The podiums are 6 feet apart, per recommendations from the Centers for Disease Control and Prevention.
Gabriella Demczuk for CNN
The debate was initially supposed to take place in Arizona with a live audience.
The debate was initially supposed to take place in Arizona with a live audience.
Gabriella Demczuk for CNN
Biden came into the debate with a significant lead in delegates. Sanders has acknowledged his path to the nomination is narrowing.
Biden came into the debate with a significant lead in delegates. Sanders has acknowledged his path to the nomination is narrowing.
Sarah Silbiger for CNN
"This is bigger than any one of us," Biden said of the coronavirus epidemic. "This calls for a national rallying."
"This is bigger than any one of us," Biden said of the coronavirus epidemic. "This calls for a national rallying."
Sarah Silbiger for CNN
Sanders said during the debate that the government <a href="index.php?page=&url=https%3A%2F%2Fwww.cnn.com%2Fpolitics%2Flive-news%2F2020-democratic-debate-live-updates%2Fh_ec7ded0cd5b9972498188272d1658145" target="_blank">should pay for all coronavirus testing and treatment.</a> "Do not worry about the cost right now," he said. "Because we're in the middle of a national emergency."
Sanders said during the debate that the government should pay for all coronavirus testing and treatment. "Do not worry about the cost right now," he said. "Because we're in the middle of a national emergency."
Sarah Silbiger for CNN
A camera crew gets a closer look at the candidates.
A camera crew gets a closer look at the candidates.
Sarah Silbiger for CNN
Another behind-the-scenes view of Sunday's debate.
Another behind-the-scenes view of Sunday's debate.
Gabriella Demczuk for CNN
The two candidates stand farther apart than normal while posing for photos before the debate.
The two candidates stand farther apart than normal while posing for photos before the debate.
Gabriella Demczuk for CNN
The moderators look over notes during a commercial break. From left are CNN's Jake Tapper, Univision's Ilia Calderón and CNN's Dana Bash.
The moderators look over notes during a commercial break. From left are CNN's Jake Tapper, Univision's Ilia Calderón and CNN's Dana Bash.
Gabriella Demczuk for CNN
Biden and Sanders bump elbows at the start of the event.
Biden and Sanders bump elbows at the start of the event.
Gabriella Demczuk for CNN
Tapper looks at his phone before the debate.
Tapper looks at his phone before the debate.
Gabriella Demczuk for CNN
Workers wipe down the podiums before the debate.
Workers wipe down the podiums before the debate.
Sarah Silbiger for CNN
The moderators' table is cleaned and disinfected.
The moderators' table is cleaned and disinfected.
Sarah Silbiger for CNN
The stage is cleaned before the debate.
The stage is cleaned before the debate.
Sarah Silbiger for CNN