For Joseph R. Biden Jr., campaigning these days means virtual fund-raisers. Shuttered field offices. And rallying support by live stream, a tactic vulnerable to severe technological difficulties, as he discovered on Friday evening.

As the sound cut in and out and the audio often came out garbled, Mr. Biden sought to host what his campaign had called a “virtual town hall with Illinois,” in which he spoke to supporters and voters via video in place of an originally scheduled Chicago get-out-the-vote event — or at least, that was the goal.

“I’m sorry this has been such a disjointed effort here because of the connections,” Mr. Biden said as he wrapped up his final answer, to a question about whether he supports the Endangered Species Act. (He does, he said. “Oh, I love you,” the questioner replied.) “There’s a lot more to say, but I’ve probably said too much to you,” Mr. Biden added.

As the nation confronts the coronavirus crisis, the presidential candidates are facing a new challenge to their pursuit of the Democratic nomination: how to connect with voters during the height of the presidential primary campaign — from a safe distance. Both Mr. Biden and Senator Bernie Sanders, his chief rival in the primaries, have had to pull back from large-scale events this week and allow their staff members to work from home.