Washington, DC – The role of the vice president in the United States is often seen as limited in scope, but the names of vice presidential candidates still appear on ballots, yard signs, and campaign materials alongside their presidential counterparts.

While the Constitution grants the vice president limited powers, their influence can be significant in the White House, helping to promote the campaign's message and providing support.

This year, President Joe Biden is anticipated to retain Vice President Kamala Harris as his running mate. Former President Donald Trump is expected to reveal his VP choice around the time of the Republican National Convention next month.

The vice president is elected alongside the president, which means a vote for Biden is also a vote for Harris for another term.

As the election season ramps up, Al Jazeera examines the vice presidency in the US and the selection process for vice presidential candidates.

What is the Vice President's Role in the Constitution?

Christopher Devine, a political science professor who has authored two books on the topic, explains that the constitution assigns a "very limited set of responsibilities" to the vice president.

“The VP takes over for the president in case of death, resignation, or temporary incapacity. That's the significant one,” Devine told Al Jazeera.

The vice president also casts tie-breaking votes in the Senate, a role Harris frequently fulfilled in the initial years of Biden's presidency when the Senate was evenly divided.

Although the vice president presides over the Senate, this duty has become largely ceremonial.

What Does the VP Do Beyond Official Duties?

Modern vice presidents often serve as advisers to the president, being the “last person in the room” before major decisions are taken, according to Devine.

“They act as liaisons to Congress, assist in legislative negotiations, and are involved in foreign policy tasks, such as meeting foreign leaders and attending state functions,” he said. “Much of what vice presidents do is not constitutionally mandated.”

Who Defines the Role of the VP?

The influence of vice presidents has varied in modern history, with figures like Dick Cheney being highly influential, while others like Mike Pence maintained a lower profile.

Devine emphasized that the president determines the vice president's role.

“Presidents have the discretion to use their vice presidents as key advisers or marginalize them. It varies from administration to administration,” he said.

Lindsay Chervinsky, a historian, noted that a vice president's experience and connections also affect their influence. Cheney, for example, had extensive governmental experience before becoming VP.

“Vice presidents need relevant skills and contacts to exercise significant influence,” she said.

How are VP Candidates Chosen?

Unlike presidential candidates, VP hopefuls do not participate in party primaries. They are selected after the presidential candidate is chosen.

Presidential nominees select their running mates, who are then officially nominated during the party convention.

Devine mentioned that the vetting process for VP candidates is thorough, involving interviews, tax, and medical records checks.

“They delve deeply to ensure there are no hidden issues that could surface during the campaign,” Devine explained.

What Do Presidential Candidates Look for in a Running Mate?

Chervinsky noted that being a strong public speaker and an effective “attack dog” against opponents are desirable traits in a vice presidential pick.

“Candidates usually seek someone different in terms of race, age, gender, and experience to balance the ticket and widen electoral appeal,” she added.

Biden’s choice of Harris, a younger Black woman, contrasted with his own demographic. Similarly, Obama selected Biden, who had decades of Senate experience, to complement his own profile as a first-term senator.

Besides election strategies, candidates look for VPs who can assist in governance once in office, Devine said.

Do VP Picks Matter in Elections?

Both Devine and Chervinsky believe VP candidates generally do not determine the outcome of campaigns.

“Their impact mainly lies in how they reflect on the presidential candidate's judgement,” Devine noted.

What About Trump’s VP Pick?

Trump's relationship with his former VP soured after Pence declined to contest Biden’s electoral victory during his ceremonial role in Congress.

“Trump seeks a loyal running mate who aligns with his priorities, potentially a woman or person of color to appeal to diverse voters,” Chervinsky said.

Reported VP candidates for Trump include Congresswoman Elise Stefanik, Senator Tim Scott, Senator JD Vance, and North Dakota Governor Doug Burgum. Scott is the sole Black Republican in the Senate.

“While ideally, a VP should complement governance capabilities, that may not be Trump's primary criterion,” Chervinsky remarked.