She will be sworn into office on Dec. 12.
Caruso, in a statement, said the voters had spoken, but he was proud of his campaign.
"There will be more to come from the movement we built, but for now, as a city we need to unite around Mayor-elect Bass and give her the support she needs to tackle the many issues we face," Caruso said. "Congratulations, Karen, and Godspeed."
Caruso held the lead in the vote count after Election Day, but as updates slowly trickled in over the next week, Bass surpassed him and then gradually extended her lead.
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Bass was working in her Los Angeles congressional office when she learned that The Associated Press had called the race Wednesday afternoon. In a statement, Bass said she received a "gracious call" from Caruso. Bass said she hopes Caruso "continues his civic participation in the city that we both love."
The Bass campaign provided a photo of Bass sitting at a desk in her office, watching television coverage of her victory, with a framed newspaper clipping of when Barack Obama won the presidency in 2008 leaning against the side of the desk.
"The people of Los Angeles have sent a clear message: it is time for change and it is time for urgency," said Bass, the first sitting House member to be elected mayor of Los Angeles since 1953, when Rep. Norris Poulson was elected. Then-Reps. James Roosevelt, Alphonzo Bell and Xavier Becerra lost campaigns for mayor in 1965, 1969 and 2001.
Outgoing Mayor Eric Garcetti called Bass' victory a "historic moment and a win for all Angelenos." Garcetti said Bass had received "unconditional support" throughout the transition period and has already begun preparing with his team on the transfer of power.
The race tightened in the weeks before Election Day, with Caruso closing the gap in several polls after trailing by as many as double-digits among likely voters as late as October, according to a Los Angeles Times/UC Berkeley Institute of Governmental Studies poll. Heading into Election Day, several experts described Bass as the favorite, though they were uncertain how much Caruso's spending would sway the race.
But Bass, who positioned herself as the authentic, pro-abortion rights Democrat in the race, won over an electorate that experts said favored her. The mayor of Los Angeles has no power over abortion. Caruso was a Republican until 2019 and donated to anti-abortion politicians, allowing Bass to contrast herself as a "lifelong, pro-choice Democrat" in a city that leans heavily Democratic.
Bass was also endorsed by nearly every major figure in the Democratic Party, including Obama, President Joe Biden and Vice President Kamala Harris.
"People do vote the party line now more than ever, in this very hyper- polarized state we're in," Mindy Romero, director of USC's Center for Inclusive Democracy, told City News Service.
Romero added that Bass' mainstream endorsements, name recognition and lengthy history in Los Angeles made a difference.
Bass inherits leadership of a city grappling with a scandal that has embroiled City Hall for the past month, after three council members and a top county labor official took part in a recorded conversation in October 2021 that included racist comments and attempts to manipulate redistricting.
Combined with concerns over homelessness, crime, quality of life and cost of living, "people are just the most pessimistic I've seen Angelenos in basically a decade and a half -- since the Great Recession," according to Guerra.
Bass, 69, grew up in the midst of the Civil Rights Movement with three brothers in the Venice and Fairfax neighborhoods. She was drawn to community activism after watching the movement on television, volunteering for Robert F. Kennedy's 1968 presidential campaign when she was 14.
Her organizing career began in 1990, when she founded Community Coalition, a South Los Angeles social justice group in response to the crack cocaine crisis.
In 2004, Bass was the only Black woman in the Legislature when she was elected to the Assembly. Four years later, she became the first Black woman to lead the chamber. Bass was elected to the House of Representatives in 2010.
Bass was considered by Biden to serve as his running mate when he was running for president in 2020, a position that eventually went to Harris.