As President Biden works his way back from Covid, let us spare a thought for Vice President Harris. She’s a heartbeat away from the Oval Office, under the oldest president and among the frailest presidents we’ve ever had.

Vice presidents straddle that thin EKG line and since We-the-People ride it along with them, we expect them to follow the Boy Scout motto: “Be prepared.”

In the early days of our republic, vice presidents earned no respect for this role. Like your appendix, they were noticed only when something went wrong.

When it did, you could live without one, just as for 200 years America didn’t bother to fill vice-presidential vacancies — and until the 20th century, candidates gave little thought to the job.

In 1876, upon learning that the Republican convention had chosen Congressman William A. Wheeler as his running mate, the presidential nominee, Rutherford B. Hayes, wrote to his wife, “I am ashamed to say: Who is Wheeler?”

Our first no. 2, John Adams, wrote of this thankless job, “I am vice president, yes. And in this, I am nothing. But I may be everything.”

His president, George Washington, was healthier than Mr. Biden, who has survived brain aneurysms, cancer, and Covid-19. Ms. Harris is younger but served only a few years in the Senate upon acceding to the vice presidency.

It seems a no-brainer that Mr. Biden would teach her what he learned in his half century of public service. Instead, the two remain estranged.

Last November, the Sun wrote about CNN’s report that the Biden-Harris relationship had “collapsed” into what “West Wing aides are calling ‘entrenched dysfunction.’” 

President Eisenhower, recognizing his advanced years, created the modern vice presidency for Richard Nixon, whom he gave opportunities to grow on the world stage.

This might not have any constitutional basis. The sole job of the vice president is as a member of the Senate, of which he or she is president.

As the Sun has pointed out on a number of occasions, the vice president is not an aide to the president. The veep can’t be fired by the president or told what to do. 

Americans, though, like some rainy-day planning. Candidate Biden promised to host his vice president for lunch once a week, just as President Obama did.

Once elected, though, Mr. Biden didn’t break bread with Ms. Harris until almost six months into his term and did so just twice in the first four months of this year.

Another vice president, Millard Fillmore, was also iced out of the cool kids’ table. When he was thrust into the presidency in 1850 (on the death of President Taylor), the entire Cabinet resigned, all with secession in the air over slavery.

If all this drama sounds a little too “Mean Girls” for a modern White House, there’s more. Mr. Biden continues to dump intractable problems, like the southern border, in Mrs. Harris’s lap.

This is setting up a veep to fail in a way unseen since Vice President Hamlin — whom President Lincoln replaced on the ticket — got Vice President-elect Andrew Johnson drunk before he swore to the Constitution.

Such tom-foolery might have fallen out of fashion once our enemies started splitting atoms, just as it’s no longer enough for a president to leave the keys on his desk and no roadmap of where to go.

Mr. Biden admires FDR, and this is a rare opportunity to surpass him. If the prospect of spending time with Mrs. Harris is too off-putting, he might remember an incident when he and Mr. Obama were senators.

While Mr. Biden was giving one of his rambling speeches, Mr. Obama passed someone a note reading, “Shoot. Me. Now.”  Regardless of this boredom, Mr. Obama as president kept lunch with Joe on his weekly schedule on his schedule because he knew that his vice president had to be informed, confident, and ready to lead. 

Mr. Biden owes it to the nation to overcome any reluctance and ensure that his veep is just as prepared to take the wheel as he was. After all, today, Ms. Harris is nothing. But one day, she may be everything.