FILE - Sen. Kamala Harris, D-Calif., waves to another member of the committee during a hearing on Capitol Hil in Washington, Oct. 3, 2018.
FILE - Sen. Kamala Harris, D-Calif., waves to another member of the committee during a hearing on Capitol Hil in Washington, Oct. 3, 2018.

COLUMBIA, S.C. - As Americans commemorate Martin Luther King Jr.'s contributions to the nation, Democratic presidential hopefuls are fanning out across the country to honor the civil rights leader.

Sen. Kamala Harris, D-Calif., used the holiday to launch a presidential campaign that, if successful, would make her the first woman and the second black candidate to become president.
 

FILE - Sen. Cory Booker (Democrat-New Jersey) spea
FILE - Sen. Cory Booker (Democrat-New Jersey) speaks at a get-out-the-vote event hosted by the NH Young Democrats at the University of New Hampshire in Durham, New Hamshire, Oct. 28, 2018.

Meanwhile, an annual rally to observe King's birthday held in the capital of South Carolina, a critical early-voting state in the Democratic primary, will feature two senators expected to seek the White House in 2020, Cory Booker of New Jersey and Bernie Sanders of Vermont.

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Former Vice President Joe Biden, who's weighing his own presidential bid, is set to speak at a King holiday event in Washington alongside former New York mayor and possible 2020 rival Michael Bloomberg. Two candidates who have already opened exploratory committees — Sens. Elizabeth Warren of Massachusetts and Kirsten Gillibrand of New York — will also appear at King-centered events.
 
While the Democratic field for 2020 is only beginning to take shape, the year that would have marked King's 90th birthday gives the party's prominent members a valuable opportunity to address race and, potentially, draw a contrast between their own views and those of President Donald Trump, whose approach to questions of racial justice has sparked criticism from multiple minority groups since he took office.
 
How Democratic contenders, both those officially in the race and those still mulling campaigns, celebrated the King holiday:
 
Kamala Harris
 
Harris, a first-term senator and former California attorney general known for her rigorous questioning of Trump's nominees, opened the holiday by declaring her bid on ABC's "Good Morning America." She abandoned the formality of launching an exploratory committee, instead going all in on a presidential campaign.
 
"I love my country," she said when asked what qualifies her for the presidency. "And this is a moment in time that I feel a sense of responsibility to stand up and fight for the best of who we are. And that fight will always include, as one of the highest priorities, our national security."

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Harris, 54, is a daughter of immigrant parents who grew up in Oakland, California. She cited her years as a prosecutor in asserting: "My entire career has been focused on keeping people safe. It is probably one of the things that motivates me more than anything else."
 
The senator plans a formal campaign launch in Oakland in a week and will have her headquarters in Baltimore. She's already planning her first trip to an early primary state as a declared candidate. On Friday, Harris will travel to South Carolina to attend the Pink Ice Gala in Columbia, which is hosted by a South Carolina chapter of the Alpha Kappa Alpha Sorority, which Harris pledged as an undergraduate student at Howard University. The sorority, founded more than 100 years ago, is a stronghold in the black community.