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WASHINGTON — Sen. Kamala Harris, D-Calif., announced on Monday that she will run for president in 2020, becoming the third senator since December to enter what is likely to be a crowded Democratic primary field.

“I am running for president,” Harris, the first African-American to formally enter the 2020 fray, said on an early-morning Martin Luther King Jr. Day interview on ABC’s “Good Morning America."

“This is a moment in time where I feel a sense of responsibility to stand up and fight for the best of who we are,” she said.

If elected, Harris, the daughter of an Indian mother and a Jamaican father, would be the first woman president and the first woman of Asian or African American heritage to hold the White House. The Harris campaign noted that her announcement not only coincided with Martin Luther King Jr. Day, but also fell on the same week 47 years ago that Shirley Chisholm became the first black woman to launch a bid for a major-party presidential nomination.

Although the timing of Harris’s announcement was intended to underscore the historic elements of her candidacy, she brushed off questions about her background at a Monday afternoon press conference, responding that she chose to identify as "a proud American."

Harris also tweeted an announcement video on Monday and launched a campaign website that teased a slogan, "Kamala Harris For The People," a nod to her career as a prosecutor. Additionally, she invited supporters to attend an official announcement event in her hometown of Oakland, Calif., on Sunday, Jan. 27.

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“Truth, justice, decency, equality, freedom, democracy: these aren’t just words, they’re the values we as American cherish. And they’re all on the line now,” Harris said in her announcement video. “Let’s claim our future.”

A campaign spokesperson said that within 30 minutes of her announcement, Harris had received donations from individuals in all 50 states.

In the video, Harris invites viewers to attend a campaign event in her hometown of Oakland, Calif. on Sunday, Jan. 27.

Harris, 54, is unusual among likely 2020 presidential contenders in that she entered the national spotlight largely after President Donald Trump’s election.

With a high-profile perch on the Senate Judiciary Committee, she earned a following among Democrats for her methodical cross-examinations of the administration’s cabinet and judicial nominees, especially during Justice Brett Kavanaugh’s closely watched confirmation process.

On policy, she has tacked toward the progressive end in the Senate, including signing onto a Medicare For All bill backed by Sen. Bernie Sanders, I-Vt. Her own legislation includes the LIFT Act, which would create a monthly tax benefit as high as $500 for working families, and a bill with Sen. Rand Paul, R-Ky., that would encourage states to reform their cash bail system.

Harris has also put a heavy emphasis on immigration, including calling on Homeland Security Secretary Kirstjen Nielsen to resign after changes to administration policy led authorities to separate children from their parents at the border.

As a career prosecutor, Harris won her first campaign in 2004 for San Francisco district attorney. She then went on to serve as California attorney general before winning a Senate seat to replace Barbara Boxer in 2016.

However, her past legal career is likely to come under scrutiny in the Democratic primary, where voters have grown more skeptical of law enforcement amid a wave of activism centered on police misconduct and racial disparities in the justice system.

Harris has described herself as a “progressive prosecutor” who spent her career focused on addressing systemic inequality, improving relationships between police and minority communities, and protecting marginalized groups from hate crimes.

“It is a false choice to suggest that communities don't want law enforcement. Most communities do,” Harris told ABC Monday morning, adding that “our system of justice has been horribly flawed.”

But not everyone is convinced that Harris can transcend her tenure as California’s chief law enforcer.

She has faced recent criticism from the left for her push to criminalize parents whose children skip school and her decision to defend the state’s death penalty in court despite her personal opposition to capital punishment.

The Republican National Committee was quick to seize on the left's divide over Harris’s prosecutorial record, with a post-announcement statement dubbing her “the least vetted Democrat running for president” and adding that “her hometown paper says she was a bad manager as attorney general.”

The Harris campaign will be headquartered roughly an hour north of Washington in Baltimore, with a second office in Oakland, Calif. Juan Rodriguez, who managed Harris’s 2016 Senate run, will again serve as her campaign manager.