The vice president’s office in the West Wing has many benefits, but it almost always fails to propel its occupant directly to the oval one down the hall. Vice President Harris is confronting just how hard it is to earn that promotion. Her struggle — emerging from the shadow of a president she serves and chart a fresh course — has no easy solution.

“It’s been a long time, Marty,” President George H. W. Bush said after winning the 1988 election to succeed President Reagan. He referred to President Van Buren, the previous incumbent vice president to win elevation — and, as presiding officer of the Senate, certify his victory — under President Jackson in 1836.

Presidents and vice presidents began running on the same ticket after the 12th Amendment was ratified in 1804. Since then, a dozen incumbents have tried to make the veep leap. President Nixon in 1960, Vice President Humprey in 1968, and Vice President Gore in 2000 carried their party’s banner but lost. The others fell short of being nominated by either of the two major, national parties.

Humphrey is the closest analogue to Ms. Harris. A last-minute replacement for the unpopular President Lyndon Johnson, who surprised the nation by deciding not to seek reelection, Humphrey entered the race after the primary season concluded and was nominated by a convention held at Chicago as was the one this year.

A fight for the nomination might have pushed Ms. Harris to lay out policies distinct from President Biden, something she has struggled to do. On Tuesday, a host on “The View” asked if she’d have “done something differently” than Biden. “There is not a thing,” she replied, “that comes to mind.”

Mr. Biden’s approval rating, 40 percent in FiveThirtyEight, is lower than Johnson’s 49 percent in his final Gallup rating. Van Buren and Bush benefited from serving under chief executives the public liked rather than being dragged down by ones they didn’t, but even well-liked bosses weren’t enough for Nixon or Mr. Gore.

Complicating the situation is that the qualities that bring a president victory — voter support, charisma, and luck — are like airline tickets: Nontransferable. Scandals and failed policies, meanwhile, tend to prove stickier. With the usual dynamics at play, a president has sympathy for this and backs his vice president to the hilt, seeing their success or failure as a reflection of his legacy.

Mr. Biden, though, was forced out and a president commands the nation’s focus until his term ends. Even an offhand remark could prove devastating for a would-be successor. In the heat of the 1960 campaign, a reporter for Time, Charles Mohr, asked Eisenhower for “an example of a major idea” he’d adopted from Nixon. “If you give me a week,” Ike said with a chuckle, “I might think of one.”

The press erupted into laughter, but Nixon wasn’t amused. Ms. Harris can’t be joyous about how Mr. Biden is conducting himself, either. His unfulfilled promise to stump brings to mind how he pledged to host her for lunch once a week — a courtesy he was extended as President Obama’s backup — only to abandon the idea after he won.

While other former Democratic presidents and presidential nominees stump for Ms. Harris, Mr. Biden is hanging her out to dry in a way reminiscent of Ike’s joke. The AP reported last week that “Biden pledged to campaign hard for Harris” but is “mostly a no-show.” On August 31, he announced a Labor Day event at Pittsburgh and said he’d be “on the road from there on.”

Instead, Mr. Biden has ghosted Ms. Harris. He may be trying to do her a favor by staying out of sight, but if that’s his goal, he’s failing in the execution. His first visit to the press room last week upstaged a major Harris campaign event, one of several times he’s bigfooted her.

On Sunday, Axios described the relationship between Mr. Biden and Ms. Harris as “increasingly fraught” according to “10 people familiar with the situation,” with some on the vice president’s team saying the White House isn’t “sufficiently coordinating Biden’s messaging and schedule to align with what’s best for the vice president’s campaign.”

If Mr. Biden is unwilling to help and Ms. Harris can’t find a way to Monday morning quarterback his record, the fate of others who peaked at number two in the executive branch looms. Expect Democrats to point fingers at both the president and vice president if Ms. Harris loses next month, leaving Van Buren and Bush as the only members of their exclusive White House club.