Former President Barack Obama endorsed Sen. Dianne Feinstein, D-Calif., on Friday in her re-election bid.

“She’s always been an indispensable leader for California, and we became dear friends and partners in the fight to guarantee affordable health care and economic opportunity for everybody; to protect our planet from climate change, and our kids from gun violence,” Obama said in a statement. “I ask Californians to join me in supporting Dianne Feinstein’s re-election and returning one of America’s most effective champions for progress to the Senate.”

Feinstein is facing state Sen. Kevin de Leon in the Democratic primary. Though de Leon has faced fundraising challenges, he received a boost last month when billionaire liberal donor Tom Steyer endorsed him.

According to the most recent campaign finance report filed with the Federal Election Commission, de Leon currently has more than $670,000 cash on hand.

Feinstein, meanwhile, has more than $10.3 million cash on hand, according to the FEC.

Obama and Feinstein, 84, served in the Senate together from 2005 to 2008. Feinstein was first elected to the upper chamber in 1992.

“It means a great deal to me to receive President Obama’s endorsement, and I’m thankful and honored for his trust,” Feinstein said.

The California Democrat called Obama a “singular president with a remarkable legacy that will truly stand the test of time.”

Feinstein has received endorsements from a number of top Democrats, including former Vice President Joe Biden, Sen. Kamala Harris, D-Calif., former Sen. Barbara Boxer, D-Calif., and House Minority Leader Nancy Pelosi, D-Calif.