Former Vice President Joe Biden and Vermont Sen. Bernie Sanders meet for their first one-on-one debate Sunday at an extraordinary time in a nation where nerves are running high as Americans hunker down at home in an effort to slow the spread of the novel coronavirus.The CNN debate, which was initially scheduled to take place in Arizona, will be held at 8 p.m. ET in the network’s bureau in Washington, D.C., with no audience. It comes at a pivotal point in the race — following Biden’s surge in the delegate count over two Super Tuesday contests — as both candidates attempt to portray themselves as a capable potential commander-in-chief who could calmly steer the nation through crisis.For weeks now, Sanders and Biden have struggled to operate their campaigns in the shadow of the fast-moving virus as the number of cases in the United States has topped 3,000. The government’s calls