Analysis | The potential and risks of turning to Kamala Harris

Vice President Kamala Harris quickly emerged as the Democratic frontrunner to take on Donald Trump in the hours after President Joe Biden stepped down Sunday, fundamentally reshaping the presidential race at lightning speed.

Now the race has morphed into an abbreviated 106-day sprint, more akin to the snap elections in Europe than the lengthy American contests. The tight schedule will amplify any missteps M^me Harris, but will also minimize tripping hazards.

And in a race that Trump was poised to win, Harris immediately becomes the ultimate X-factor.

Mr. Biden quickly endorsed M.^me Harris, who would be the first woman, the first Black person and the first person of South Asian descent to serve as president. As the Democratic Party rallies behind her — the loudest dissenting voices were simply those who didn’t publicly support her — here are six reasons why her candidacy is both promising and perilous.

She reverses the age argument.

During the Republican primaries, Nikki Haley warned everyone who would listen that the first party to replace its octogenarian nominee—Mr. Trump will be 80 years in office if elected to a second term—would win. She was making that argument for herself, but the logic applies to Ms.^me Harris.

Unlike Mr. Biden, who is 81, Mr.^me Harris, 59, is not old — and that simple fact neutralizes what has been one of Mr. Trump’s most potent lines of attack.

In the minutes after Mr. Biden left office, Democrats and anti-Trump Republicans alike questioned Mr. Trump’s ability to govern into his 80s, a bold attempt to reframe a debate about age that has been so damaging to Democrats.

“She can make the issue of age and fitness a liability for Trump,” said Erin Wilson, Ms.’s deputy chief of staff.^me Harris, during a phone call Sunday with the group Win With Black Women.

She is a former prosecutor. Trump is a convicted felon.

Harris has often been at her political best when she has taken on the role of chief prosecutor, whether in debates when she first attacked Biden in June 2019 over organizing school busing to promote social diversity (busing) or as a senator on the Judiciary Committee, where her intensive cross-examinations went viral.

When she ran for president, one of her catchphrases — and her troubled campaign tried several — was that she was best placed to “prosecute the cause” against Mr. Trump.

She will have the opportunity to do so in the same year that a New York prosecutor obtained 34 criminal convictions against him and as Mr. Trump still faces more than one future criminal trial.

People who have worked with M^me Harris believes the framework could allow her to play to some of her strengths and expose some of Mr. Trump’s weaknesses. Polls have shown that a sizeable share of voters believe Trump has committed crimes, but still intend to vote for him.

Biden was “Scranton Joe.” Harris will be seen as a California liberal.

While Mr. Biden was widely considered too old to lead, he had other advantages accrued over his 50 years in the public eye. In particular, he was long seen as a moderate Democrat who stood up to the most extreme elements in his party. That helped him appeal to the political center.

“Do I look like a radical socialist who has a weakness for rioters?” he fumed at one point in the 2020 race. His image was such that Republicans sometimes chose to attack him by suggesting that he was being led by other forces.

M^me Harris does not have this advantage.

Instead, M^me Harris got her start in politics as a district attorney in one of the country’s most liberal cities, San Francisco, before winning a seat in one of the country’s most liberal states, California. (Mr. Trump, among others, was a donor at the time.)

What if M^me Harris has not established a reputation as an outspoken progressive in California — her slogan as a prosecutor was to be “smart on crime” — but when she ran for president in 2020, she regularly took positions to the left of Mr. Biden, including by embracing a “Medicare for all” plan that he had avoided implementing.

As Joe Biden’s partner for three and a half years, Mr.^me Harris must also support the agenda of a president who has become deeply unpopular.

Trump’s team has already indicated that it plans to attack him on immigration in particular. The question is whether Mr.^me Harris can successfully campaign on some of the most popular accomplishments of the Biden-Harris administration without the current unpopularity of the man who previously led the ticket.

It gives Democrats a much-needed boost.

Donald Trump and his advisers weren’t looking to upset a race he was winning by almost every measure. Republicans gathered in Milwaukee last week were downright gloating about the direction of 2024, seeing Trump as a candidate all but certain to doom days after surviving an assassination attempt.

His team must now reorient itself to run a very different race against a very different candidate.

M^me Harris has the ability to energize the Democratic base — especially some key groups that had felt alienated — in a way that Mr. Biden no longer seemed able to. The president has struggled, relative to his 2020 performance, with Black voters and young voters in particular, groups against whom Harris’s historic candidacy would seem able to do better.

In a sign of Democrats’ appetite for change, donors donated more than $60 million online Sunday, the third-largest day in ActBlue’s history.

It is also notable that Mr. Trump has cast doubt on whether a future debate with Mr.^me Harris, who had rushed to share the stage with Mr. Biden, suggested a change of venue, from ABC to Fox News.

His genre could galvanize Democrats, but also Republicans.

In the 2020 primaries, Democratic voters wrestled for months over who would be the best candidate to face Trump. They questioned, often out loud, the idea of ​​nominating a woman.

Trump, after all, had just defied expectations and defeated Hillary Clinton in 2016. The party ultimately chose an older white man in Biden.

For most of the Trump presidency and beyond, Democrats enjoyed a gender gap. Women voted for Democrats by a larger margin than men voted for Republicans. But Trump increased his advantage with men so much that the gender gap suddenly favored the GOP.

M^me Harris has the potential to reverse that trend and has already proven herself to be a far more compelling messenger than Mr. Biden on the issue that Democrats believe can win them the 2024 race. Mr. Biden rarely uttered the word “abortion”; M^me Harris visited an abortion clinic.

M^me Harris faces other unique challenges as a Black and female candidate, in a country and political system where the two groups are often held to different standards. And in Trump, she faces an opponent who has a history of exploiting stereotypes to his advantage.

It can be transcendent, but also hesitant.

One of the highlights of M’s rapid rise^me Harris’s rise to the top of Democratic politics in just over a decade is the few loyalists who stuck with her to the end.

While Biden has surrounded himself with a small, sometimes insular, coterie of advisers—a recent addition to Biden’s inner circle could have served him for a decade—Harris has relatively few longtime aides. Early in her tenure as vice president, her team has undergone significant turnover.

She has few advisers, even when she was in the Senate, and even fewer when she was California’s attorney general. She parted ways with much of her senior team during her 2020 presidential primary campaign, which was marked by infighting.

Those who have worked for and against her say she has few equals when she delivers a grand speech or a scathing retort in a debate or committee hearing. But they also say she can get worked up, fall back on clichéd comments and make self-inflicted errors of hesitation.

Now she inherits Mr. Biden’s massive campaign apparatus. And she has just over 100 days to secure both the Democratic nomination and the presidency.