If he's elected, Joe Biden will become the 15th US vice president to reach the White House, and the first since George HW Bush more than 30 years ago.
The role of the vice president has evolved over time, progressing from a somewhat undistinguished position to a sought-after office viewed as a springboard to the presidency.
Fourteen previous vice presidents took over through death, nomination or resignation.
As election day draws nearer, the eyes of the American people are just as much on Mike Pence and Kamala Harris, Donald Trump and Joe Biden's running mates, as they are on the main candidates themselves.
So, what is the definition of the vice president?
Dr Joel K Goldstein, a scholar of the vice presidency, presidency and constitutional law, says: "Initially, the role of the vice president was very simple.
"The traditional arrangement was the constitution gives the vice president two roles.
"The vice president is the president of the Senate and has a tie-breaking vote when the Senate is tied, and the vice president stands first in the line of presidential succession."
The position has evolved to become an important part of the presidency - and an important part of a president's success or failure in office.
"The vice president's principal function and purpose is to provide high-level assistance to help make a presidency succeed," Dr Goldstein says.
"The description that I've just given of the vice president's role is one that has developed.
"It wasn't always this way, but this has been more of the development of an evolutionary pattern that has taken place in American public life.
"The vice presidency, while it can be looked at as an office in and of itself and a story in and of itself, is also an example of the way in which American political and governmental institutions can evolve and take on roles that are more consequential and different than what was perhaps initially intended."
In the 19th Century and for around half of the 20th century, the vice president was a "legislative officer" and often was not compatible with the serving president.
"Vice presidents from John Adams, our first vice president, to Alben Barkley, who was Harry Truman's vice president from 1949 to 1953, spent most of their time presiding over the Senate. They took on really little or no function in the executive branch," Dr Goldstein says.
"Vice presidents during this period, up until the middle of the 19th century and middle of the 20th century, were typically chosen by party leaders for the national ticket.
"The presidential candidates had little or no influence in choosing their running mates."
It also wasn't seen as a role for someone politically ambitious.
"When Daniel Webster, who was one of our great statesmen in the first part of the 19th Century, the former senator from Massachusetts and secretary of state, when he was offered the chance to be the vice presidential candidate on the ticket in 1848 with Zachary Taylor, he declined, saying, 'I don't propose to be buried until I'm dead'," Dr Goldstein explains.
However, this perception began to change with Richard Nixon, whose time as vice president was occupied with taking on assignments from then president Dwight Eisenhower.
Dr Goldstein says: "The reason for the change that began with the Nixon vice presidency really related to larger changes in American life.
"With the New Deal and the Second World War, the national government became more important.
"It became important that the presidential successor be somebody who was informed and who was well thought of.
"So, beginning with vice president Nixon, the vice president became an occasional presidential adviser who attended national security meetings and other meetings occasionally in the White House."
Subsequently, the role has developed into one of the best ways of becoming a candidate for the presidency.
"Before Nixon, vice presidents typically didn't end up as presidential candidates. Beginning with Nixon, they almost always did," Dr Goldstein says.
Perhaps the most significant change began with the presidency of Jimmy Carter and vice presidency of Walter Mondale in 1977.
"In the Carter administration, the vice president was brought into the White House itself and vice president Mondale became part of president Carter's inner circle," Dr Goldstein explains.
"In this new model of what I've called the White House vice presidency, which began with president Carter and vice president Mondale, it has really been followed ever since, with some variations, but on a bipartisan basis by the administrations that have followed during the last 44 years."
The office has developed not just because of the idea of succession but with the goal of making the president succeed.
Modern-day examples include vice president Pence taking on the role as chair of the taskforce on coronavirus. Similarly, during the Obama administration, vice president Biden was in charge of disengagement from Iraq and negotiating budget and tax agreements.
"He (Biden) often took on the role that most vice presidents had taken on: of being willing to tell the president things that oftentimes were critical of the president, or that the president might not want to hear," Dr Goldstein says.
(He made) sure that the president was getting a full spectrum of advice. That's what I think is significant about this change from being a legislative office, then an office that was primarily about presidential succession, to one that is more about being an executive office and being part of the inner circle of the White House, one that's designed to help make presidents succeed.
"By and large, this change has taken place without any change in our constitution, without any change in our laws."
But while vice president Pence and senator Harris could well see their role as a stepping stone to the presidency, election, or even presidential nomination, is far from certain.
Al Gore narrowly missed out to George W Bush in 2000 despite winning the popular vote and Mr Mondale lost to Ronald Reagan in a 1984 landslide.
As Dr Goldstein explains: "It's early to know what things will look like in 2024. A lot can change in four years."