“The task is, are you able to cut through?” Mr. Margolis said. “Are you able to cut through when Americans are consumed by a virus that is in the news, and that’s all that’s being discussed, whether on the Senate floor, the White House briefing room or in emergency rooms?”

Some Democrats have been perplexed at why Mr. Biden has not used his newfound free time to blitz television news shows, many of which are enjoying high ratings with so many people confined to their homes. He did not do any of the Sunday morning news programs and has also been absent from daytime cable news, which has been dominated by the daily briefings of Mr. Trump and Mr. Cuomo.

On Monday, a day after one of his own donors asked how he could become a bigger part of the national conversation, Mr. Biden gave a speech that was streamed live from his home in Delaware in which he criticized Mr. Trump’s response to the virus as too slow and insufficient, and pressed him to act like the “wartime president” he says he is.

But his address offered a reminder of the continuing challenge he faces in getting attention, even when he does speak out. CNN, Fox News and MSNBC did not air his speech, instead showing a briefing by Mr. Cuomo of New York.

“The whole country is focused on one issue and one issue only,” said Teddy Goff, who served as a top digital strategist for the campaigns of President Barack Obama in 2012 and Hillary Clinton in 2016. “It’s certainly going to be very difficult to break through on other issues. But it’s essential for the person who’s highly likely to be our Democratic nominee to have a strong voice on this issue.”