President Biden, nearing the end of his run on the world’s biggest stage, is leaving Democrats to recast their nominee. To get more Americans to cheer and not jeer the swap, the party needs to look no further than their TVs.

Vice President Harris now has enough delegates for the nomination, but any president is a tough act to follow — and for Mr. Biden’s term, he’s treated her as a background extra. That makes “passing the torch” a tougher sell.

On Monday, the White House had Mr. Biden “appear” with Ms. Harris by voice only, due to Covid. It seemed odd with Zoom and FaceTime ubiquitous, but at least she didn’t pretend to speak to him on a prop phone. That lazy trick for absent actors always inspires eye rolls.

A famed Hollywood producer, J. Michael Straczynski, planned his sci-fi series, “Babylon 5,” with foresight the White House could have used. For major characters, he wrote “trap doors,” players ready to step into their shoes. It’s the exact role the Constitution delegates to the vice president.

“It seems a no-brainer,” I wrote for the Sun in August 2022, that Mr. Biden would teach Ms. Harris “what he learned in his half century of public service. Instead, the two remain estranged.” In November of 2022, CNN reported that their relationship had “collapsed.” The weekly lunches Mr. Biden promised never materialized.

Like many vice presidents, Ms. Harris languished in obscurity, tasked with the job of Border Tsar and little else. With few flashbacks of accomplishments for a clip show, to all but the party faithful, she just dropped into a long-running program.

That has been the case before, but this is different. Mr. Biden won all the 2024 primaries, his fourth campaign, before his withdrawal. Ms. Harris steps in not as president, but as the first candidate in 100 years not voted on by the public.

Complicating the transition, Mr. Biden has canceled all trips for the next two weeks. His renowned backslapping skills will be put to the test when he emerges. People will sense if there’s friction with Ms. Harris.

Consider “Bewitched.” The first actor to portray Darrin Stephens, Dick York, withdrew due to a back injury. The studio brought in a lookalike, Dick Sargent, who lacked the same chemistry with Darrin’s on-screen wife, Samantha. At Sitcoms Online, viewers prefer York to Sargent 81 percent to 6 percent.

As I wrote in the Sun two weeks ago, the TV actor, Rob Reiner, forgot that this is often the case in calling for Mr. Biden’s replacement. “Whenever producers changed the actor portraying a character,” I said, “fans revolted.”

My example was Michael Evans, who portrayed Lionel Jefferson on “All in the Family” and its spinoff, “The Jeffersons.” When he was “replaced by Damon Evans, to whom he bore no relation and little resemblance, the new actor was rejected.”

The actress who portrayed Jan Brady on “The Brady Bunch,” Eve Plumb, wouldn’t commit to “The Brady Bunch Hour” variety show. The job went to Geri Reischl, derided by fans for 50 years as “Fake Jan.”

When the star of “Chico and the Man,” Freddie Prinze, died, in stepped a 12-year-old, Gabriel Melgar, saving the final season. By contrast, when Fonzie emerged as a fan favorite on “Happy Days,” writers deleted the eldest of the Cunningham children, Chuck, without bothering to offer an explanation.

In the series finale, Howard Cunningham — originally a father of three — said he’d had “the joy of raising two wonderful kids,” as if Chuck never existed. This trope lives in infamy as “Chuck Cunningham Syndrome.” Audiences don’t like to be played for fools.

The men who succeeded the first James Bond, Sean Connery, were accepted because they made the role their own rather than insulting fans with cheap Connery impressions. Ms. Harris will have to hew closer to 007 and young Chico if she hopes to win the presidency.

Audience loyalty cannot be transferred like delegates; it must be earned. Be mindful of that, and Ms. Harris increases the odds that Americans will embrace her in this new role. Take their support for granted and be a political Chuck Cunningham — forgotten as America’s story goes on without her.