Harris - who made the announcement on Martin Luther King Jr. Day - joins Senator Elizabeth Warren of Massachusetts, Hawaii congresswoman Tulsi Gabbard, New York Senator Kirsten Gillibrand and former housing secretary Julian Castro, among others, either in the race or exploring a run for the 2020 Democratic nomination.
Nearly 22 months before the 2020 election, the battle for the White House is already firming up, as Americans begin to assess who might be the opposition party nominee to challenge Trump for control of the White House. Harris's calls for unity in her newly published memoir - "The Truths We Hold: An American Journey," from Penguin Press - clearly set the tone for what a Harris candidacy might mean in an America sorely divided by Trump's unsettling presidency.
After two terms as district attorney of San Francisco (2004-2011), she was twice elected as attorney general of California (2011-2017), becoming the first woman and the first black person to serve as chief law enforcement officer of that populous state.
Then in January 2017, she took the oath of office as California's junior US senator, making her the first woman of South Asian descent (her mother is a Tamil Indian) and only the second black woman senator in American history, after Carol Moseley Braun.
Her focused and often tough-sounding lines of questioning during closely watched Senate hearings reflect her past as a prosecutor.
Harris often proudly recalls that as a prosecutor she fought big banks during the 2008 financial crisis. She casts herself as a champion of middle class families "living paycheck to paycheck" and denounces police brutality and the killing of unarmed black men.