Harris's policy positions - Medicare for all, progressive tax reform, raise in the federal minimum wage, green energy, etc. - are not unique in a field with many progressive candidates.
She is unique because of her biography - a daughter of immigrants from India and Jamaica, who spent years as a prosecutor and then state attorney-general - and her personal appeal.
Of those candidates already declared, she might be the most engaging and dynamic.
While she is better known for her prosecutorial questioning on the Senate Judiciary Committee, she has come across as bubbly, warm and fun on her book tour.
The comparison to President Barack Obama - a child of mixed race, a new senator, a charismatic speaker, an aspirational message - is obvious.
More so than Obama, however, she stresses an inclusive message, aiming for an America where everyone is "seen" and feels he or she has a place.
And in contrast to Obama's cool and reserved persona, Harris radiates warmth and stresses her connection to friends, family and community.
Unlike Warren, who has been wowing crowds with an emphasis on a policy-laden progressive agenda, Harris has very deliberately made her personal story a key component of her message.
We thankfully haven't seen trips to the dentist (she is not afflicted with the over-sharing syndrome). However, her book The Truths We Hold, among the best campaign books I've had to endure, highlights the influences that shaped her (her mother; being raised in California's dynamic African-American community) and her political ascent as a lawyer and politician.
The book attempts to pre-empt criticism of her tenure as prosecutor as insufficiently progressive. The attacks, she says, set up a "false choice" between tough prosecution of violent crime and criminal justice bias, especially in the fruitless war on drugs.
Her prosecutorial background in a general election would likely be an asset, not a detriment. She'll have to find a way to defend herself without sounding defensive. Compared with Gillibrand's challenge in explaining a sweeping ideological shift from Blue Dog to progressive, however, Harris's task is modest.
Harris' greatest strength, which if she is as smart as she seems should be at the centre of her campaign, might be her ability to talk about politics in terms of values - empathy, fairness, personal responsibility.
The only politician I've seen to do this as effectively is on the GOP side, former Ohio Governor John Kasich.
In a country exhausted and disgusted with Trump's degradation of his office and normalisation of cruelty, bigotry and xenophobia, Harris's description of an America people can be proud of has great appeal. Americans should be discussing big issues. What does it mean to be an American?
Harris will enter the race as less well known than Warren and some others, but potentially with more upside.
She has less experience on a national stage but greater opportunity to define herself. She'll be a formidable contender.
