Former Vice President Joe Biden and Sen. Bernie Sanders sought in Sunday’s Democratic debate to cast themselves as best-positioned to lead the nation through a global pandemic, with Biden pledging to deploy the military to help with recovery efforts and Sanders using the crisis to pitch his long-sought overhaul of the country’s health care system.

The fast-moving coronavirus dominated the first one-on-one faceoff of the 2020 campaign, reflecting the way the crisis has upended American life by closing schools, disrupting travel and raising questions about President Donald Trump’s ability to lead the nation through turbulent times.

“This is bigger than any one of us — this calls for a national rallying for one another,” Biden said.

Biden’s and Sanders’ prescriptions for addressing the public health and economic crisis highlighted the ideological divide between the two men vying for the Democratic nomination. Biden, a centrist who helped implement the 2009 bailout of the financial industry, warned that another government-backed economic rescue plan may be needed in the coming months, while the liberal Sanders suggested a tax on the wealthiest Americans.

The stakes and the standings in the race for the Democratic nomination have shifted dramatically since Biden and Sanders last debated less than three weeks ago. After a sluggish start to the primary season, Biden has surged to the front of the field, drawing overwhelming support from black voters and consolidating the backing of several rivals who have dropped out of the race.

Biden appeared determined to keep his focus on the general election, making direct overtures to Sanders’ supporters and committing for the first time to selecting a woman as his running mate if he becomes the Democratic nominee. After Biden’s announcement, Sanders said he would “in all likelihood” do the same.

READ MORE: What to watch in the Biden-Sanders debate

Sanders has struggled to broaden his coalition beyond young people and liberals, and his path to the nomination is rapidly shrinking. Still, he appeared determined to draw sharp contrasts with Biden throughout, challenging the former vice president to disavow a super PAC backing his candidacy and casting Biden as inconsistent during his career on his support for the financial industry and women’s health issues.

The Vermont senator also repeatedly pushed questions regarding the coronavirus toward a now-familiar debate between him and Biden over health care. Sanders argued that the troublesome shortages in coronavirus tests and anxiety over the preparedness of the nation’s health care system to deal with an impending increase in patients highlight why the U.S. should move to the government-run, “Medicare For All” system he has long championed.

“One of the reasons that we are unprepared, and have been unprepared, is we don’t have a system. We’ve got thousands of private insurance plans,” said Sanders, who backs a sweeping government-run health insurance program. “That is not a system that is prepared to provide health care to all people in a good year, without the epidemic.”

Biden, who supports adding a public insurance option to the current system, argued that a pandemic was not a moment to attempt to push through an overhaul of the American health insurance system, a politically arduous endeavor.

“This is a crisis,” Biden said. “We’re at war with a virus. It has nothing to do with copays or anything.”

As the debate opened, Biden and Sanders skipped a handshake, greeting each other instead with an elbow bump. They took their positions at podiums spaced 6 feet apart in keeping with guidance from the Centers for Disease Control and Prevention for limiting the spread of the novel coronavirus. They addressed the nation, and each other, from a television studio in Washington without an in-person audience.

The pandemic has upended the campaign for days, prompting Biden and Sanders to cancel rallies and instead hold virtual events with voters around the country. Their campaign staffs are also working remotely, and the candidates — both in their late 70s — said they were taking personal precautions to guard against a virus that is a greater risk to the elderly.

“I’m using a lot of soap and hand sanitizer,” Sanders said.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

The vast majority of people recover from the new virus. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to recover. There are more than 167,000 cases confirmed worldwide.