WASHINGTON — Sen. Kamala Harris entered the 2020 presidential campaign Monday, describing herself as a “fighter” who will stick up for average Americans.

Kicking off a week that will include national television appearances, a rally in Oakland and two trips to early primary states, the California Democrat gave a preview of her campaign strategy: heavy on emphasizing “fighting ... for the people” and light on talk of President Trump.

The former state attorney general and San Francisco district attorney made her widely expected announcement in an interview on ABC’s “Good Morning America,” following that up with a news conference at her alma mater, Howard University in Washington, a historically black university.

“I love my country. And 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,” Harris said on ABC.

She kept her policy pronouncements general. Asked what her campaign’s signature issue would be, she said, “The core of my campaign is the people,” citing issues including climate change, income insecurity and bias in the justice system.

One subject Harris did not dwell on was Trump. She made only veiled and passing references to the president. Harris said the 800,000 federal workers who have been unpaid for a month during a record-setting shutdown in a dispute over funding for Trump’s border wall “don’t want a wall; they want a paycheck.”

Implicitly drawing a contrast, Harris positioned herself as a public servant.

“The American people want a fighter, and they want someone who will fight like heck for them and not fight based on self-interest, and I’m prepared to do that,” she said.

In a campaign kickoff video, Harris said she would hold a rally at noon Sunday in her hometown, Oakland, at Frank Ogawa Plaza outside City Hall. She also debuted her campaign theme: “For the People.”

Harris, 54, picked Martin Luther King Jr. Day to make her announcement, a nod to the fact that she is likely to be one of the few women of color in the race. She is the daughter of an Indian-born mother and Jamaican father who met at UC Berkeley in the 1960s and were active in the civil rights movement.

She said she was “honored” to announce on the day commemorating King’s life.

JUST IN: @KamalaHarris on announcing she will be running for president in 2020: "I feel a responsibility to stand up and fight for who we are." https://t.co/qUX1sERxxZ pic.twitter.com/NcSHFTRIny — Good Morning America (@GMA) January 21, 2019

The first-term senator joins an already crowded field of Democrats hoping to unseat Trump. In the past few weeks, her fellow Democratic Sens. Elizabeth Warren of Massachusetts and Kirsten Gillibrand of New York have announced exploratory committees. Julian Castro, a Cabinet official under former President Barack Obama and former mayor of San Antonio, is also running.

Harris enters the race in the top tier of candidates, having built a national profile in her two-plus years in the Senate. But she won’t be alone.

In addition to Warren and Gillibrand, other Democratic senators considered to be possible candidates include New Jersey’s Cory Booker, Amy Klobuchar of Minnesota, Oregon’s Jeff Merkley and Sherrod Brown of Ohio. And independent Sen. Bernie Sanders of Vermont is looking at another run for the Democratic nomination.

Former Vice President Joe Biden is also weighing getting into the campaign, as is former Rep. Beto O’Rourke, who was narrowly defeated in his Texas U.S. Senate race in November.

Harris declined to attack any of her Democratic potential opponents Monday and wouldn’t elaborate on what distinguishes her from the pack.

“I think the voters will decide,” she said. “There are already and will continue to be great candidates who are running this race, and I think the process will have much more integrity the more people who want to run.”

She said she would be traveling the country and listening to Americans’ stories. She plans to visit South Carolina, an early primary state, on Friday and do a nationally televised town hall next Monday in Iowa, the first state to hold caucuses.

Harris has tapped Juan Rodriguez to manage her campaign, reprising the role he played in her 2016 Senate race. Her campaign chair will be her sister, Maya Harris, a civil rights attorney and adviser to Hillary Clinton’s 2016 presidential campaign.

The campaign will be headquartered in Baltimore, with a second office in Oakland.

Harris’ “For the People” slogan is a reference to her courtroom introduction when she served as a prosecutor in San Francisco and Alameda counties, when she would address the court as “Kamala Harris, for the people.” Her campaign logo is designed in part as a throwback to the campaign of Shirley Chisholm, who became the first black woman to run for president from a major party when she mounted a 1972 run for the Democratic nomination.

Harris had no legislative experience before winning election in 2016 to the seat opened by former U.S. Sen. Barbara Boxer’s retirement, having spent her career in district attorney’s offices and the California Department of Justice. In Washington, she has been in the spotlight for her sharp questioning at hearings of Trump administration officials, some of whom have bristled at her pointed style.

Harris’ policy record in the Senate has trended toward the progressive Democratic base. She has been an outspoken advocate of immigration, a reflection of her constituency in California and her life story as the child of immigrants.

Harris was also the first Democrat to announce in 2017 that she would co-sponsor Sanders’ Medicare-for-all bill, which would make the federal government the single payer of medical expenses. And she has introduced legislation that would offer relief for middle- and lower-income families in the form of tax credits.

Her prosecutor background could be a liability among progressives, however, as critics have mined her record for lines of attack, including whether she was complicit in policies that disproportionately harm communities of color.

Harris addressed both her experience level and her history as a prosecutor on “Good Morning America,” saying she has “the unique experience of having been a leader in local government, state government and federal government.”

At her news conference, Harris defended her arguments as California attorney general against the state providing gender reassignment surgery for transgender inmates, saying she “had a host of (state agency) clients that I was obligated to defend and represent, and I couldn’t fire my clients.”

She said that “unfortunately,” there were times her “clients took positions that were contrary to my beliefs.”

In her ABC interview, she also noted that as a prosecutor, she represented sexual assault victims and homeowners victimized by predatory lending firms. She said the justice system “includes systemic racism” and needs reform.

“It’s a false choice to suggest that communities don’t want law enforcement. Most communities do; they don’t want excessive force. They don’t want racial profiling,” Harris said. “Our system of justice has been horribly flawed and it needs to be reformed.”

She added, “There’s a lot of work to do, but to suggest it’s one or other — no, I don’t buy that.”

Tal Kopan is The San Francisco Chronicle’s Washington correspondent. Email: tal.kopan@sfchronicle.com Twitter: @talkopan