Presidential candidates, and their campaigns, are the sum of all in which they exist and what came before them.

Just after he announced he was withdrawing from the 2024 presidential race, President Joe Biden endorsed his vice president, Kamala Harris, as the nominee in his place — giving her a huge leg up in whatever process could follow from here. But there are still many unknowns about the future of the Democratic ticket.

Over the past weeks, amid speculation about Biden's future on the ticket, two debates have played out. The first big question is whether Harris will be President Joe Biden’s replacement, or if another Democratic politician, like Govs. Gretchen Whitmer (MI), Josh Shapiro (PA), or Gavin Newsom (CA) would do better. The other question circulating among pundits, pollsters, journalists, strategists, and regular folks is whether Harris would be a stronger presidential contender than Biden.

We can answer this question in a few ways: looking at data on her prospects, her recent performance on the campaign trail, and her past candidacies. Each of these paths give us limited answers, but to borrow a phrase from former Defense Secretary Donald Rumsfeld, we can still identify a few “known unknowns” that make the future a bit more divinable.

Coconut-pilled backers of a Kamala Harris presidential campaign argue that Harris runs about even or even better than Biden does against former President Donald Trump in polling; they point to Harris’s performance on the campaign trail so far, making the case against Trump and the American right’s plans in Project 2025; and at a base level, they argue that she has been tested on the national stage, while other alternative candidates have not.

Critics of the KHive — as the online superfans of the vice president call themselves — and the VP argue that Harris is still really unpopular with the American public. They argue that the polls don’t actually show that much of an advantage for Harris in battleground states or with the popular vote; they point to her failed 2019 presidential campaign and her tepid vice presidential tenure as proof she’s not a particularly good candidate or politician and would likely run an uneven campaign.

They also argue that Biden’s flaws and foibles are already built into the electorate’s mind, while the chaos and uncertainty of swapping in Harris would expose the Democrats to even more risks (like how voters react to a woman of color as a nominee).

The debate was the roiling undercurrent of the will-he-or-won’t-he drama over Biden these last few weeks. How it resolves now that he is off the ticket could have enduring ramifications for both the Democratic Party and the country.

Harris backers have plenty to point to in the aftermath of June’s presidential debate.

There’s the obvious stuff: Harris is younger, can actually string sentences together, and has already been campaigning against Trump this year. These points were once again demonstrated this week — while Biden was forced to recover from Covid at his home in Delaware during the week of the Republican National Convention, Harris was on the trail with North Carolina Democratic Gov. Roy Cooper.

What the data says: First, a caveat: comparing polling of reality to a hypothetical match-up is always a bit treacherous.

What we can say from head-to-head polling of Harris is that the general trend has gotten a lot better for her. A year ago she was underperforming Biden in head-to-head polling against Trump in a variety of surveys. Closer to the debate and right after, she began to perform about evenly. And more recently, in July, a few polls comparing Biden and Harris against Trump in battleground states and nationally have shown Harris even with Biden or slightly ahead of him.

The first sign of this change came from CNN’s first post-debate poll, finding the vice president trailing Trump by 2 percentage points (within the margin of error) while Biden trailed by 6 points. And in FiveThirtyEight’s polls-only post-debate comparison of Harris and Biden vs. Trump, Harris performs slightly better than the president in battleground states — though not in all of them.

Recent polling from Pennsylvania and Virginia also shows more positive signs for the vice president: New York Times/Siena College polls this month show that while Harris still trails Trump by 1 point in Pennsylvania, that’s a smaller gap than the 3 points that put Trump ahead of Biden there. Both of these results are within the polling’s margin of error, making the race in the state essentially tied. In Virginia, meanwhile, Harris’s lead over Trump is 2 points larger than the lead Biden has over the former president.

And a post-assassination attempt national poll from Reuters/Ipsos shows a statistically tied presidential contest for either Biden or Harris against Trump.

Under the hood, however, Harris backers can find an additional data point in their column: 69 percent of respondents think Biden is too old; Harris doesn’t face that concern. And Biden is more unpopular than Harris, something that is consistently true: As of July 18, Biden has a net -17.7 approval rating in the FiveThirtyEight aggregate. Harris’s disapproval is at 11.8. And in RealClearPolitics’ average of favorability ratings, Biden (-16.3) is also more unpopular than Harris (-14.9)

What the campaign trail shows: Harris backers can point to the vice president’s performance on the road this year and argue that she has evolved as a politician since her presidential run in 2019, and especially since the overturning of Roe v. Wade in 2022 — when she became the White House’s go-to surrogate and messenger on reproductive rights.

She has dominated that issue, both in official visits to states where abortion and reproductive rights have been under threat, and also during campaign swings this year that have seen her become more willing to talk about the personal experiences that pushed her to become a sex crimes prosecutor and be able to connect with voters in a way Biden can’t.

At the same time, she has been playing up that past as a prosecutor — something she was not able to do during her last national campaign against fellow Democrats. “Prosecuting the case against Donald Trump” is now a go-to part of her stump speeches, both in talking about his and his party’s record on abortion and in talking about Trump’s convictions and indictments.

At the top of the ticket, she would be able to zero in on this approach against an unpopular Republican candidate.

What history tells us: Before her doomed 2020 presidential bid, Harris had a successful electoral record in California: winning statewide races by tacking to the center or simply pointing out how weird or abnormal her opponents were.

Running as a center-left politician was part of her bid during her first statewide race in California — for attorney general — since she was facing a popular moderate Republican during a red-wave year in 2010, and she was viewed as a liberal Bay Area district attorney. She opposed right-wing positions on gay marriage and immigration enforcement, and cast her opponent as an extremist, while also attacking him for not prosecuting more cases, including sex crimes.

Her 2016 Senate campaign, meanwhile, showed how she’s able to remain on message and be disciplined — winning support from the Democratic establishment, consistently holding a fundraising advantage, and showing that her Democrat opponent was not a serious candidate. There wasn’t much of a policy difference between Harris and her opponent, former Los Angeles District Attorney Steve Cooley, but she was still able to deliver a landslide win.

Even her 2020 campaign shows that she’s a pragmatic thinker — not necessarily tied to a specific ideology that influences the way she would approach issues. She fumbled on policy, and couldn’t make a distinctive, proactive case to the Democratic base in the primary, but she doesn’t have to do that now. Even during this cycle, she has shown moments of pragmatism, too — her position on the war in Gaza, for example, put her to the left of Biden on the issue — but she has found ways to speak to young progressives and voters critical of Israel’s approach while still representing the president.

What the data says: The major problem in comparing these Harris figures to Biden’s actual standing against Trump is that Biden’s numbers factor in every negative thing that he and his campaign have endured so far. Biden backers would point to the fact that opinions of Harris could still change for the worse as her theoretical campaign becomes not so theoretical anymore, and that her performing about as evenly as Biden against Trump is not that great of a sign when there is more uncertainty about how Harris would even campaign.

On that front, they point to the fact that Harris’s favorability numbers are not that different from Biden’s, and could still get worse. In recent polls, she performs worse than Biden in battleground states like Michigan, Arizona, and Nevada — losing those states would likely doom a Democratic candidate.

And she doesn’t necessarily do significantly better than Biden when looking at how subgroups of voters feel: She wins the same share of Black voters as Biden in head-to-head matchups with Trump in battleground states, per Split-Ticket.org’s polling, and does slightly worse than Biden among white voters, who still make up the majority of voters in swing states and nationally.

What the campaign trail shows: Taking the Kamala-critical position on the data as is — that there’s essentially no difference according to polls in how Harris performs against Trump than Biden — you are justified in being worried about what the campaign trail might look like.

Harris has only recently, since 2022, been active on the campaign trail, in part because she’s not the most naturally gifted campaigner or communicator. She has found the issues she excels at championing, but that’s only after going through a rocky first year as vice president when her office saw a variety of staff departures, infighting, and missteps in message.

She received media training during that first year in order to get better at talking about the president’s agenda, but still struggled to define her portfolio — facing intense criticism on immigration and the border when that wasn’t even her original assignment.

Reporters who have been covering her tenure point out that she seems most at home when she’s having more roundtable-style conversations, not necessarily in one-on-one interviews or while giving stump speeches.

Harris critics also point out that she will struggle to convince voters to see her as a legitimate candidate given biases against her because of her race, her gender, and the general idea that she’s not that plugged into the White House inner circle or aware of the day-to-day business of running the country.

And then come the memes. While the genre of Kamala Harris memes has been exploding in popularity recently because of the chaos over Biden’s own candidacy, those jokes start from a kernel of truth: Harris is an awkward communicator. She’s prone to gaffes, to awkward jokes, to tortured analogies or stories, and is generally perceived as easy to mock.

What history tells us: Harris critics also have plenty to point to when criticizing her electoral history. Her toughest race was her first race, for California attorney general, when she was the worst-performing statewide Democratic candidate on the ballot, winning her seat by about 1 percentage point.Read that again. She nearly lost to a Republican in California.

There’s the context that this was a red-wave year — the 2020 midterm elections were terrible for Democrats. But in California, she essentially had united Democratic support for her campaign, and still came close to failure — while every other Democratic candidate on the ticket performed significantly better.

She cruised to victory during the 2016 Senate race in part because the whole contest was “uninspiring,” and neither Harris nor her opponent were able to excite voters during most of the campaign because Harris’s victory was assumed from the start. She also faced an easy, flawed candidate in that race: a wacky US representative who famously “dabbed” on stage during a debate.

And her 2020 presidential contest showed what happens when a candidate lacks clarity about her campaign and reasons for running. She struggled to define herself, and her position on the ideological spectrum, relative to her Democratic rivals. She could not run a disciplined campaign — two rival camps within her operation pulled the campaign in different directions for much of the primary.

This record shows the legitimate reasons to question whether Harris would be able to make a proactive case for herself — not just a negative case against Trump. She faces the struggle of convincing voters not to blame her for the unpopular results of the Biden-Harris administration, while still thinking of her as presidential material.

That’s one edge the governors and senators who have been talked about as potential alternatives to Biden have: They wouldn’t carry the same baggage from the Biden administration. Harris will likely be seen as tied to Biden’s legacy, which stands as another reason to look elsewhere.