In a one-two upheaval in US politics, President Joe Biden has said he will not run for re-election in November and instead endorsed Vice President Kamala Harris.

Harris already made history by becoming the first Black and female vice president in US history, but has faced concerns over whether she can defeat Republican candidate and former President Donald Trump.

The coming days will show if Harris will indeed be embraced by the party and chosen as their candidate at the Democratic National Convention next month.

On Sunday, Biden called the decision to pick former prosecutor Harris for his 2020 ticket “the best decision I’ve made”, while calling on Democrats to support her.

“Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year,” Biden said in a post on X.

Here’s what we know about Harris:

Who is she?

Harris, 59, was born in Oakland, California, the daughter of an Indian-born mother and Jamaican-born father.

She attended Howard University in Washington, DC before getting her law degree from the University of California College of the Law, San Francisco.

She began working in the Alameda County district attorney’s office, before shifting to the San Francisco district attorney’s office.

She became San Francisco’s district attorney in 2003. She was then elected California’s attorney general, the state’s top law enforcement role, in 2010 and was re-elected four years later.

She was elected to the US Senate in 2016 and became a leading critic of Trump, particularly when it came to his immigration policies.

Her aggressive questioning of Supreme Court nominee Brett Kavanaugh in 2018 helped solidify her credentials as one of the Democratic Party’s top rising stars.

Harris is married to lawyer Doug Emhoff, who became the first “second gentleman” in US history following the 2020 election. Harris and Emhoff has no children.

How did she become vice president?

Harris initially mounted a run for the White House in the 2020 election, but quickly faded in the primary season after lacklustre debate performances.

As Biden solidified his lead in 2020, he vowed he would select a woman as his running mate. The selection of Harris was seen as an effort to appeal to Black voters, and to energise the party’s base.

Harris’s law enforcement credentials and centrist approach were also seen as assets that could draw undecided voters away from Trump, although her history also roiled the progressive wing of the party.

In a 2019 debate, Harris had also challenged Biden on race, a viral moment that many thought may have ended her chances of becoming the vice president once he became the party’s nominee.

How has she made history?

Harris has collected several superlatives in her career, becoming the first Black woman to hold almost every role she’s had: the district attorney of San Francisco, California’s attorney general, senator from California and vice president.

Harris was also the first daughter of immigrants ever elected as vice president.

How has she been as a vice president?

Speaking to Al Jazeera, Jennifer Victor, a professor at George Mason University, described Harris as a “very typical vice president”.

Harris has largely cheerled signature policies of the Biden administration, including infrastructure legislation, immigration, gun control and efforts to protect abortion rights.

In particular, Harris has been tasked with spearheading efforts to stem migration from Central America.

“Her popularity numbers haven’t been too high, but she also hasn’t had a lot of press coverage,” Victor said. “She has not been in the big spotlight of political discourse over the last few years … but I think what we’re going to see is a massive ramping up.”

Will she be able to beat Trump?

That remains the big question for Democrats.

Al Jazeera’s Alan Fisher, reporting from Washington, DC, said that while Biden has endorsed Harris, it does not mean she will receive support from the Democratic Party, which has less than a month until its convention starts.

“Democrats might not want to fight on the convention floor in Chicago,” Fisher said. “This looks unseemly, and so they may well quickly coalesce around Kamala Harris, and then look to put in a vice president who will perhaps help them in other areas”.

Recent polls taken after Biden’s weak debate performance against Trump have not suggested that Harris is likelier than Biden to beat Trump in November. Harris supporters have argued those polls may change now that Biden is out of the race.

For instance, an Economist/YouGov poll released last week found Biden would lose to Trump 41 percent to 43 percent. The poll showed Harris losing to Trump 39 percent to 44 percent.

A Reuters/Ipsos poll found both Biden and Harris performing the same against Trump: A statistical toss-up.

Why has she been controversial?

Harris has described herself as a “progressive prosecutor”, but she has made few inroads with the progressive wing of the party.

While Harris did oversee some reforms in her career, critics have accused her of at best taking a mixed-bag approach in her policies.

That included a controversial truancy enforcement push as San Francisco’s district attorney that saw parents face penalties for their children missing school.

Her office also worked to prevent the release of more prisoners, despite massive overcrowding in California prisons. And as the state’s attorney general, Harris argued a case defending the use of the death penalty in California, despite being personally against it.

Long hailed as the future of the Democratic Party, Harris has also faced criticism that she has not lived up to expectations. Detractors have said she lacks the charisma to rally the party.

What’s her position on Israel’s war on Gaza?

On Israel-Palestine, Harris has hewed close to the Biden administration’s “ironclad” support for Israel and she has regularly defended Israel’s right to self-defence, including during the war on Gaza.

She is set to meet with Israeli Prime Minister Benjamin Netanyahu this week when he visits the US.

Still, Harris has been one of the more vocal members of the administration highlighting the humanitarian catastrophe unfolding in the enclave. In March, she became the highest-ranking member of the administration to use the word “ceasefire” in calling for a humanitarian pause in the fighting.