Just over a week since his disastrous debate performance, Joe Biden’s approval ratings have plummeted, and a growing chorus of his Democratic colleagues are now casting doubt over the future of the US president’s re-election bid.

Vice presidents, like Biden himself, have a strong track record of going on to become their party’s presidential nominee. Yet, Kamala Harris has struggled to find her footing as Biden’s deputy, wrestling with low approval ratings and criticisms that she has underperformed throughout her tenure.

However, there are reasons to believe that many might be underestimating Harris’ potential at the top of the 2024 Democratic ticket.

She’s made a career out of prosecuting a case

Donald Trump is the first president in American history to be found guilty of felony crimes after leaving office and the first candidate in a century to campaign for president as a convicted felon.

In just a matter of days, the Republican Party will officially anoint him as their presidential nominee at the party’s national convention.

There is every sign that, like in the last election cycle, a 2024 path to Democratic presidential victory would rely on Americans turning out to vote against Trump rather than for the Democratic alternative.

Harris has spent her entire professional life making the case against individuals convicted of committing crimes. Before entering the Senate, she had a long career serving in her county office and as district attorney before making a successful bid to become California’s top prosecutor in 2010. Her skills of interrogation on the courtroom floor would serve her just as well on the presidential debate stage in a match up against Donald Trump, as they did during his impeachment hearings in 2020.

Harris may be well positioned to prosecute the Democrats’ case against Trump – namely, that he poses an existential threat to US democracy and must be kept out of the White House at all costs.

Abortion is her strongest issue – and the Democrats’

While Harris has struggled to carve out her own voice in the vice presidency, abortion is an issue where she has proved herself to be one of the Democrats’ most effective communicators.

Since the fall of Roe v Wade in 2022, Harris has delivered impassioned speeches on key anniversaries, made a historic visit to an abortion clinic, and energised the young and Black voters President Biden struggles to reach.

The fight for abortion rights is a key pillar of the Democrats’ plea that “democracy is on the ballot” for American voters in 2024, as they seek to capitalise on 2022 midterm wins and the success of state-level abortion ballot initiatives which have triumphed even in traditionally Republican states like Ohio, Kansas and Kentucky.

Yet, across his decades in Congress, Biden has a mixed record on abortion rights and continues to demonstrate some unease when talking about the topic. In the presidential debate, he trailed off and failed to effectively counter Trump on what is meant to be the Democrats’ most promising campaign issue.

With Harris at the top of the ticket, Democrats would be placing their strongest voice on their strongest issue at the forefront of voters’ minds.

The alternatives are untested at the federal level

A host of popular governors in key swing states are among the other names circulating as potential Biden alternatives. Governor Gretchen Whitmer, who featured on Biden’s 2020 running-mate shortlist, is billed as a candidate who could draw votes to the key battleground state of Michigan. In the 2022 midterms, she helped to deliver a historic Democratic trifecta hold of the state’s House, Senate and governorship for the first time since 1984.

First-term Pennsylvania Governor Josh Shapiro could help to win over some former Trump voters in the crucial swing state, which also hangs in the balance in 2024. Meanwhile, California Governor Gavin Newsom has been waiting in the wings for years, growing his electoral margins and national profile with each gubernatorial election.

But success at the state level does not necessarily translate to an ability to win votes from Americans nationwide.

Failed 2024 Republican primary contender Ron DeSantis is the prime example of this. The Florida governor struggled to break through on the national stage, despite once being dubbed 'DeFuture' of the Republican Party following his landslide reelection in 2022. While these Democratic governors have each proven themselves to be highly competent policymakers, no success at the state level can guarantee the same reception in a country of more than 300 million.

Harris, on the other hand, would inherit the Biden administration’s legislative wins and war chest, and the name recognition that comes with being a sitting vice president.

Replacing President Biden with Kamala Harris as the Democratic nominee no doubt carries risks of its own. Harris would have to undergo a quick transformation to build a presidential style distinct from the Biden-Harris brand – and more convincing than her failed 2020 run, which ended before a single Democratic primary vote was cast – while also contending with increased public scrutiny due to her race and gender.

But in an election that will likely come down to just thousands of votes in a handful of states due to the Electoral College system, sticking with Biden at the top of the Democratic ticket might prove to be the greatest risk of all.