When the former vice president announced his pick, Long Beach Mayor Robert Garcia said his heart was filled with "optimism and happiness" after what he called a rough couple of weeks in the wake of the death of his mother and stepfather to COVID-19.
Garcia was sworn in as mayor in 2014 by Harris, who at the time was the state attorney general.
He also served as California co-chair of Harris' presidential campaign.
MORE: Joe Biden selects California Sen. Kamala Harris as running mate
"Congratulations to the next VP of the United States, Kamala Harris! So proud of our Senator and hopeful for the future of our country," Garcia tweeted.
Congratulations to the next VP of the United States, Kamala Harris! So proud of our Senator and hopeful for the future of our country. I’ve supported her from day one because she has the integrity and character to lead. Thank you VP Biden for making this incredible choice. pic.twitter.com/vAlCUrVloK— Robert Garcia (@RobertGarciaLB) August 11, 2020
Los Angeles Mayor Eric Garcetti and Harris worked together on Barack Obama's presidential campaign in 2008. He said he was "over the moon" about the selection.
Garcetti was a co-chair of the search committee that helped Biden select his running mate.
"I've seen her heart, where she cares so deeply for Americans no matter who they are or where they come from," Garcetti said.
Rep. Karen Bass (D-Los Angeles), another contender to be Biden's running mate, wrote in a tweet that Harris "is a great choice for Vice President."
"Her tenacious pursuit of justice and relentless advocacy for the people is what is needed right now," Bass' tweet said.
Orange County Rep. Katie Porter also expressed her enthusiasm for Biden's selection.
"Having worked with @KamalaHarris, I know she is a fierce fighter for working families, who'll bring her tenacity to the White House," Porter tweeted.
Having worked with @KamalaHarris, I know she is a fierce fighter for working families, who’ll bring her tenacity to the White House. I’m proud of our Senator and the other #AmbitiousWomen considered and ready to work with them to defeat Donald Trump and Mike Pence. Let’s do this!— Katie Porter (@katieporteroc) August 11, 2020