There are a lot of reasons Vice President Kamala Harris would be the obvious successor to President Joe Biden if he decides not to run again this year.

Whether he actually will has been an open question since Biden’s disastrous debate performance on June 27, when he stumbled over his answers, offered non sequiturs on different topics, and failed to communicate key achievements. Those missteps came amid heightened scrutiny of his age, and were followed by recent press appearances where he’s confused the names of major figures, and offered hard-to-follow answers.

All that’s led to discussion among pundits and grassroots Democrats alike about who would fill in for Biden with just under four months until Election Day. Michigan Gov. Gretchen Whitmer has been a popular suggestion, as has California Gov. Gavin Newsom.

But perhaps no one makes as much sense as Harris, who’s already in a role designed to take over for a president unable to continue their duties.

As VP, she’s steeped in the policy work of this administration, and has extensive experience in the White House that she could bring to the job. And she could well be an energizing candidate for many Democratic voters as the first Black and South Asian woman to have the party’s presidential nomination, and as a younger, charismatic alternative to the 78-year-old Republican nominee, former President Donald Trump. Logistically, it would also be fairly easy to transfer Biden’s $91 million in campaign funds to Harris (and more difficult to hand that money over to someone else).

That said, Harris has real vulnerabilities — which have been evident during her tenure as VP and as a 2020 presidential candidate — that could potentially bog her down. Notably, her favorability ratings have sometimes lagged Biden’s while she’s been vice president, and a common critique she faces is that she hasn’t been able to carve out a distinct lane for herself. When she ran for the presidency in 2020, she fielded similar issues, leaving people confused about what she stood for.

Taken together, there’s still a strong argument for Harris to step in, if Biden drops out of the race. Notably, though, there are also some key challenges she’ll have to overcome.

If Harris were to take over for Biden, she’d have some version of the incumbency advantage as the sitting vice president. Though there are important caveats, as detailed by my colleague Andrew Prokop, roughly two of three incumbents have won reelection.

As part of that advantage, Harris would be able to tout her role in the Biden administration’s wins — like the Inflation Reduction Act, which will help lower prescription drug costs and invest in climate initiatives, and the Bipartisan Infrastructure Law, which includes historic funding for bridges and roads. She’d be able to point, too, to the experience she’s garnered as vice president and how it’s prepared her to become commander-in-chief.

It’s a strategy Biden himself successfully employed in 2020, when he linked himself to the Obama administration’s achievements — and emphasized how he was often the “last one in the room” when key decisions were being made.

“When you think about all these legislative pieces that were passed in Congress, the vice president was part of the conversations with the president, with the Cabinet, whether it was the infrastructure bill, or the IRA, or the CHIPS bill,” former Labor Secretary Marty Walsh, who’s worked alongside Harris, previously told Vox. That experience, in itself, is significant and invaluable.

Since the fall of Roe, Harris has also taken on the mantle of abortion rights, meeting with advocates and voters across the country, and rallying people on the issue in places like Wisconsin, Arizona, and Florida.

This subject has been particularly motivating for Democratic voters and women in recent elections, with multiple ballot initiatives — like those in Vermont and Michigan — passing with overwhelming support. During the 2022 midterm elections, protecting reproductive rights was a central policy for many voters, and a decisive one that helped boost Democrats. Harris’s defense of abortion access is a point that would allow her to paint a sharp contrast with Trump, who has taken credit for Roe’s demise and argued that abortion should be decided on a state-by-state basis.

In addition to the experience she has in the White House, Harris also brings legislative expertise from her four years in the Senate, and background on criminal justice reform from her time as attorney general in California. Although some of her tenure as vice president has been plagued with communications missteps, she’d previously been known for her viral moments questioning Trump appointees as a member of the Senate Judiciary Committee and made a big splash in 2019 during a debate confrontation of Biden over his past stance on busing.

Harris could infuse the ticket with new energy as well. Numerous polls have found that majorities of Americans don’t want Biden on the ballot, including a July 2024 PBS News/NPR/Marist survey placing that number at 56 percent, and want to see options other than Biden or Trump.

Harris could potentially be that alternative. At 59, she’s decades younger than both the current nominees. And she’s also emblematic of both an increasingly diverse Democratic Party and country, making her a candidate who could be especially motivating for key voting constituencies including Black women. (In a July 2024 YouGov poll, Harris’s favorability numbers were at 41 percent with adults overall, and 69 percent among Black respondents.) That could bode well for better turnout and enthusiasm.

“She’s the second Black woman elected to the Senate, which in a state like California is no small feat,” says University of Maryland public policy professor Niambi Carter. “So she’s shown that she can get voters, white, Black, Latino, and others, to come to the polls.”

Experts note, too, that bypassing Harris for another candidate — especially a white one — could run the risk of fracturing support from Black voters and other key Democratic constituencies, says Lakshya Jain, the CEO of electoral analysis site Split Ticket.

“I think there would be significant voter backlash,” Jain told Vox. “It would rupture the party and create negative news cycles for quite a while, and the eventual nominee would emerge quite wounded and with a massive amount of ground to make up among Black voters.”

Finally, on the logistics front, Harris would be able to make the transition a bit more seamlessly because she could inherit Biden’s fundraising apparatus and campaign staff, as former White House press secretary Jen Psaki explained in a TikTok post. “Structurally, she could just move the campaign staff, she could move all their resources over,” Psaki noted.

For all the strengths she’d have as a nominee, there have also been issues Harris has struggled with as vice president, and as a presidential candidate in 2020. And those could haunt her should she be Democrats’ 2024 presidential nominee.

Notably, while she’s remained liked by a number of Democratic constituencies, her overall favorability and approval numbers haven’t been the strongest. As a FiveThirtyEight aggregation found, Biden has 37 percent approval from all US voters, while Harris has 38 percent. And she’d be seen as a continuation of the Biden administration, meaning she could be simply viewed as “more of the same” by voters who aren’t happy with the policies or positions it’s represented. Per surveys from this past year, voters are interested in change and have expressed discontent with the status quo.

Harris also hasn’t always defined herself — and what she stands for — that clearly.

In 2020, that was evident in how she sought to adopt both progressive and moderate policy stances, seemingly losing members of both constituencies. She’s especially struggled with the left and its often younger voters: Despite her self-described position as a progressive prosecutor, she was called out by grassroots progressives during the 2019 campaign for actions she’d taken on truancy as well as wrongful convictions.

This same overarching issue has emerged in her vice presidency, when some critics have argued that she hasn’t established what issues she owns or been clear about what she’s been able to achieve.

White House officials have previously highlighted her extensive work on foreign policy, immigration, voting rights, and reproductive rights. That’s a broad portfolio, and staffers who’ve worked with her have described the catch-22 that it can feel like Harris faces: if she chose solely to work on one issue, for example, she risks getting pigeonholed. If she works more broadly, as she has opted to do, she’s criticized for not being dedicated to just one area.

And though she’s been an effective communicator in a number of high-profile cases ranging from her questioning of former Trump Attorney General Jeff Sessions to a major speech she gave on the 50th anniversary of Roe, she’s also been pilloried for statements that have been commonly derided as sounding like “word salad.” Those remarks have prompted some to wonder if she’d be able to be a strong enough messenger for Democrats during this pivotal time.

Her record with staff has been scrutinized by reporters, too, due to the turnover that’s taken place in her office across the roles she’s held, raising questions about her management style. Stories emerged about her attorney general office and her VP office detailing what some staffers describe as a difficult work environment that stemmed from the top. Such reports fuel concerns about what leadership would look like in a Harris White House, though her office is far from the only one to have seen turnover in these roles.

And latent sexism and racism among voters is a key worry some Democrats have raised. “I don’t know that a lot of people want to admit this, [but] I think there are a lot of people who are uncomfortable with a Black woman being the president,” says Carter. Candidates of color and women, including former President Barack Obama, have long had to navigate such biases — and electability concerns — though he was ultimately able to win in spite of them.

Overall, these dynamics indicate that a Harris nomination, like any other, would come with both pros and cons. In the difficult situation that Democrats find themselves in, Harris’s strengths could well outweigh her vulnerabilities — if she can address them.