An estimated 20,000 people came out to Frank Ogawa Plaza in Oakland on Sunday to watch U.S. Sen. Kamala Harris formally kick off her 2020 presidential campaign.

Standing in front of an Oakland City Hall decked in American flags and draped in red, white and blue, Harris spoke about her Oakland roots, her past as a prosecutor and her vision for the country.

"It was just a couple blocks from this very spot that nearly 30 years ago as a young district attorney I walked into the courtroom for the very first time and said the five words that would guide my life’s work: Kamala Harris, for the people," Harris said, explaining her campaign slogan. She returned to theme often in her speech, and it seemed to connect with rallygoers.

"It's easier to feel a personal connection her because she talks about herself," said Leili Taeb, who immigrated from Iran to San Francisco.

Harris also talked often about President Trump, calling his proposed border wall a “medieval vanity project” that would not stop transnational gangs. In addition to border security, Harris took aim at the administration's detention of migrant children, starting a refrain of "that’s not our America."

Harris cited her parents, both civil rights activists and immigrants who came to the United States to pursue higher education, as instrumental in establishing her moral compass.

"I am not perfect. Lord knows, I am not perfect," Harris told the crowd. "But I will always speak with decency and moral clarity and treat all people with dignity and respect."

She noted her support for several key Democratic issues over the course of her speech: taking action on climate change, supporting immigrants, gun control, universal health care and reproductive rights. She also touched on Americans’ economic struggles, from debt to unequal pay for women and women of color.

"When we lift up the women of our country, we lift up the children of our country," Harris said. "We lift up the families of our country. And the whole of society benefits."

Some in the diverse crowd filling Frank Ogawa Plaza came from beyond the Bay Area to hear Harris speak.

"This is the most serious and important election of my lifetime," said Julia Martinez, 33, who drove up from San Diego for the rally. "We have a great diverse Democratic field. I'd be happy with a lot of people, but Kamala is the person that when she announced, really touched me in my spirit. I will hit the streets for this person. I will walk alongside her."

The crowd also included several elected officials including Oakland Mayor Libby Schaaf, San Francisco Mayor London Breed and Assemblywoman Buffy Wicks. Schaaf endorsed and introduced Harris, and Wicks cited Harris' compassion as a key part of her candidacy.

"I think she represents everything that is not Donald Trump: emotionally, physically, intellectually," Wicks said.

Harris, 54, first announced her intention to run for president on Martin Luther King Jr. Day on "Good Morning America."

She joins an already crowded field of Democratic hopefuls including Sens. Kirsten Gillibrand (NY) and Elizabeth Warren (MA), and former Housing and Urban Development Secretary Julián Castro. Former Vice President Joe Biden, Sen. Bernie Sanders (VT) and others are also expected to join the race in the coming weeks.

Harris enters the race with distinct advantages and challenges.

In her favor are her ability to potentially build a strong coalition with key Democratic party constituencies, her fundraising capabilities and her membership on the U.S. Senate Judiciary and Intelligence Committees, both of which provide her with a national platform.

Harris could also benefit from the relatively early California primary on March 3, 2020, especially if she does well in the contests before that, including ones in Iowa, New Hampshire and Nevada.

"People are not going to vote for someone in California just because they're from California," said Democratic consultant Bob Shrum. "That person has to establish themselves and Kamala Harris will have to establish herself in those first primaries as one of the major competitors."

Harris's potential liabilities as a presidential candidate include her records as San Francisco district attorney and California attorney general. Throughout her law enforcement career, Harris has portrayed herself as a "smart on crime" and a "progressive prosecutor," themes she returned to early in her speech on Sunday.

"I knew our criminal justice system was deeply flawed," Harris said of her early days as a lawyer. "But I also knew the profound impact law enforcement has on people’s lives, and it's responsibility to give them safety and dignity."

She highlighted her work as district attorney establishing prison diversion programs and her efforts to take on Wall Street during the Great Recession as California's attorney general. In 2003, Harris defeated incumbent District Attorney Terence Hallinan with a promise not to seek the death penalty — ever.

Keeping that promise came at great personal and political cost, when months into her first term as district attorney a San Francisco police officer, Isaac Espinoza, was shot and killed on duty. Even before his funeral, Harris announced she would not seek the death penalty for his accused killer. It created a firestorm within the law enforcement community, a breach she spent the next decade repairing.

But her "progressive prosecutor" label has already come under fire, including from a few protesters at Sunday's rally.

"What it suggests is that it is a label that she desires because it is an attractive label, but it is a label that does not fit," said law professor Lara Bazelon, who heads up the Criminal Justice Clinic and the Racial Justice Clinic at the University of San Francisco. "I truly hope she stops calling herself a progressive prosecutor because it is just not accurate."

Bazelon points to Harris' refusal to support legislation requiring police to wear body cameras and another bill requiring the attorney general — the office she held at the time — to investigate officer-involved shootings. She was also slow to support legalizing the recreational use of marijuana. Harris also declined to take a position on Proposition 47, a progressive measure that reduced some non-violent crimes from felonies to misdemeanors. Voters approved it in 2014.

"What I hope we have in a president is someone who isn't afraid to be a true leader and take some brave courageous stances even if they're not sure that a crowd of people preceded them and are falling behind them," Bazelon said.

Putting all that in the balance, Harris's law enforcement record could pose the biggest problem if she wins the nomination and her opposition to the death penalty becomes the focus of her Republican opponent.

Of course that's a challenge she'd be happy to take on.