Ms Harris, 54, who is a rising star in the party, is the daughter of immigrants from Jamaica and India. They divorced when she was 7, and Kamala and her sister Maya, a civil liberties activist, grew up with their mother, who was granted custody of the children by court-ordered settlement.
"The future of our country depends on you and millions of others lifting our voices to fight for our American values", the former prosecutor and Attorney General of California said in the video. Because it is true we are a country that - yes, we are flawed, we're not flawless, but we are a great country when we think about the principles on which we were founded.
Last week, a widely-circulated New York Times op-ed written by Lara Bazelon, a law professor and the former director of the Loyola Law School Project for the Innocent in Los Angeles, argued that Harris can not be considered a "progressive prosecutor" given her record as attorney general in California.
"I think it is a false choice to suggest that communities do not want law enforcement", Harris said. "And they're all on the line now", Harris said in the video, teasing her official kickoff in her birthplace of Oakland next Sunday.
She plans a formal campaign launch in Oakland on January 27.
Popular data analysis website FiveThirtyEight wrote in response to her announcement that Harris "has the potential to be among the strongest contenders in the 2020 Democratic field".
Meanwhile, former Starbucks chief executive Howard Schultz is considering a run as an independent candidate, CNN reports.
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Harris's announcement makes her the first Indian American woman to run for USA president ever - from either party.
But she'll have plenty of rivals, some of whom are better-positioned to appeal to the ascendant economic-populist wing of the Democratic Party. She said he had a realistic idea of America's flaws, but remained "aspirational".
Harris's 13-year record as a district attorney and California's attorney general has prompted criticism from progressives who argue she wasn't tough enough on banks, and fought to uphold convictions tainted by exculpatory evidence.
"It makes me nervous", Sessions said. Since then, she has worked to establish a national profile - by aggressively questioning President Trump's judicial nominees, writing a book and stumping for Democrats in last year's midterm elections.
Her campaign will focus on reducing the high cost of living with a middle-class tax credit, pursuing immigration and criminal justice changes and a Medicare-for-all healthcare system.
The kickoff state of Iowa has a strong base of liberal activists and the race will move quickly to more diverse states such as Nevada and SC.
Harris has done little to hide her presidential ambitions. She later celebrated when it was struck down, and later fondly recalled marrying same-sex couples, thumbing her nose at her duty as California's lawyer.
Harris, who voted against Mnuchin's confirmation as head of the Treasury, has said she "followed the facts" in declining to prosecute.