White House hopefuls Joe Biden and Bernie Sanders launched a joint attack on Donald Trump’s response to the coronavirus pandemic as they faced off in a high-stakes debate Sunday, accusing the president of undermining his own scientists with misinformation.

The two rivals also sparred about their record, taking advantage of the first one-on-one format of the marathon campaign to engage in extended—though civil—policy clashes on everything from universal health care and climate change to deportations and foreign policy.

But with Biden appearing to have a good night, riding high as the frontrunner following three weeks of strong performances in multiple primaries, the 77-year-old made a splash by saying he will “commit” to picking a female running mate if he is the Democratic nominee.

Sanders said he would “in all likelihood” do the same, following the most diverse nomination contest in US history that saw no fewer than six women in the running to take on Trump in November. Going head to head days before four large states hold Democratic primaries, the two main candidates left in the race stood six feet (1.8 meters) apart and elbow bumped one another at the start of a televised debate held with no live audience as a virus precaution. Sanders, the 78-year-old underdog, took a stinging shot at the president, accusing him of fomenting confusion and eroding public trust in a time of crisis. “We have to shut this president up right now because he’s undermining the doctors and the scientists who are trying to help the American people,” Sanders added, referring to multiple Trump statements at odds with expert views.

“It is unacceptable for him to be blabbering unfactual information that is harming the American public.” Biden essentially agreed, saying: “the existential threat to the United States of America is Donald Trump.”

With the debate overshadowed by the fast-moving health crisis, Biden and Sanders spent the first half-hour on how to address the pandemic which has already caused almost 70 deaths and more than 3,600 coronavirus cases nationwide.

“We’re at war with the virus,” said the former vice president.