Six months into the coronavirus, most Americans are in the same boat as Mr. Putnam, 79, their entire worlds shrunk into neighborhoods, households, computer screens. Yet they are also preparing to undertake that most communal of obligations, a national election, during an extraordinarily polarizing presidency that has only grown more so during a pandemic that has killed nearly 200,000 Americans and a widespread movement protesting police violence and systemic racism.

More profoundly, it is not clear how social distancing will affect voters’ choices. Before the coronavirus, according to Mr. Putnam, even the most prolific online networker, with his four-hour-a-day Facebook habit, still likely had one foot in the physical world, where he discovered and tended to his relationships.

Spouses, parents and close friends — those with whom one enjoys “strong ties,” in the jargon — exert the most powerful pull on voters’ behavior. Ms. Sinclair pointed to a study based around the 2010 midterm elections that found most of a person’s Facebook friends had no impact on his voting behavior. Only his closest 10 friends, out of 150, did. In fact, he was only likely to be influenced by someone who had tagged him in a photo.