Their encounter is Retro Report’s main focus, notably the story line that swiftly took root. It held that Kennedy won on good looks alone, that against a light backdrop he appeared crisp and commanding in his dark suit while Nixon, recovering from an injury, looked pale and sweaty, his bearing hardly improved by an ill-chosen gray suit. Those who saw none of that and only listened on radio — a far more common situation in 1960 America than today — believed Nixon had triumphed. So the story went.

Many scholars have debunked that narrative, among them David Greenberg, a professor of history, journalism and media studies at Rutgers University. In the Retro Report video, Professor Greenberg contends that Kennedy’s overall performance, not just his looks, won the day. He showed, as a senator, that he could hold his own again a sitting vice president. As for Nixon’s supposedly prevailing on radio, the evidence for that is skimpy because, Professor Greenberg noted, no scientifically rigorous surveys were done at the time.

(Whatever the reality, Nixon felt burned by the experience and came to view television warily — until he ran again for president in 1968, this time successfully, tutored in the art of the camera by a young producer named Roger Ailes. Mr. Ailes, ousted in July as chairman of Fox News, is once again a media mentor, for Mr. Trump.)

When it comes to substance, and not just a stumble here or a clever line there, can a debate make or break a candidacy? Experts have long been divided. Some consider the debates decisive. That view was offered last month by Gary May, a University of Delaware historian, who wrote on the Daily Beast website, “For good or ill, television’s laserlike eye reveals the candidates’ fitness for the presidency.”

Well, maybe not, suggests another academician, John Sides, an associate professor of political science at George Washington University. Writing in Washington Monthly in 2012, Professor Sides said, “Scholars who have looked most carefully at the data have found that, when it comes to shifting enough votes to decide the outcome of the election, presidential debates have rarely, if ever, mattered.”

Even blunders may not be self-evident right away. Mr. Frankel acknowledged that he himself had not immediately recognized the damaging potential of Ford’s “no Soviet domination” remarks. Many other Americans also failed to see it until newspaper and television analyses shaped their consensus that a serious presidential slip had occurred.

These days, voters no longer need to wait for received wisdom to form. They can get it, or at least what passes for wisdom, in real time by watching squiggly lines on their television screens that represent focus group impressions of the candidates, or by following an avalanche of opinions put forth by the commentariat on Twitter and other social media.