Kamala Harris faces fellow Democrat Loretta Sanchez, a 10-term congresswoman in the November polls.
US President Barack Obama and Vice President Joe Biden today backed California's Indian-American Attorney General Kamala Harris to be the state's next Senator.
Barack Obama praised 51-year-old Kamala Harris as a "lifelong courtroom prosecutor" who has fought international gangs, oil companies and the big banks responsible for the mortgage crisis.
"Kamala Harris fights for us. That's why I'm so proud to endorse her for United States Senator," the president said in a statement released by the Harris campaign and the Democratic National Committee.
Harris faces fellow Democrat Loretta Sanchez, a 10-term congresswoman in the November polls.
"And if you send her to the Senate, she'll be a fearless fighter for the people of California - all the people of California - every single day," Barack Obama said.
Vice President Joe Biden said the Senate "needs people like her - leaders who will always fight to make a difference and who never forget where they come from."
For Sanchez, the Orange County congresswoman, the endorsements are a stinging rebuke and another political obstacle to the many she must overcome by the November election, the Los Angles Times reported.
Kamala Harris, who was born in Oakland, California, is the daughter of an Indian mother who emigrated from Chennai in 1960 and a Jamaican American father.
The president's nod caps a string of major endorsements for Harris, the candidate of choice among the Democratic Party's power barons and some of the left's most influential interest groups. It also sends a clear signal to Democratic donors, many of whom have stayed on the sidelines this election, the paper said.
Kamala Harris already has won the support of California Governor Jerry Brown and the California Democratic Party, along with Senator Elizabeth Warren (Democract from Massachusetts), a favorite of the left.
Kamala Harris said she was honoured to receive the support of the president and vice president, calling them "incredible leaders for our nation."
She has more than a 3-to-1 edge over Sanchez in fund-raising and easily topped a crowded field of Senate candidates in the June primary. The attorney general also held a 15-percentage-point lead over Sanchez in the latest Field poll, the paper said.
The two Democrats will face off in the November election, setting the stage for the highest-profile contest between two members of the same party since California adopted a top-two primary election system.
Kamala Harris' ties to Obama and his administration stretch back more than a decade, even before he burst onto the national political scene. While she was still the San Francisco district attorney, Harris supported and raised money for Obama when he ran for the US Senate in Illinois. She later served as the California co-chair of his upstart 2008 presidential campaign.
Barack Obama reciprocated by helping to launch Kamala Harris into the national spotlight when he gave her a speaking role at the 2012 Democratic National Convention in North Carolina.