California Gov. Jerry Brown tells Democrats the nomination fight is over

California Gov. Jerry Brown said Tuesday that he's supporting Hillary Clinton over Sen. Bernie Sanders for president, delivering a clear signal to Democrats to stop bickering over the nomination and focus on November's election.

The endorsement by Brown, who is respected by progressives and popular in the state, is a valuable asset for Clinton one week before the delegate-rich Democratic primary there, in which both candidates are going for broke.

His main message was for the party's factions, that it's time to acknowledge that the nomination battle is effectively over.

"Clinton's lead is insurmountable and Democrats have shown-by millions of votes that they want her as their nominee," Brown said in a statement on his website titled "An open letter to California Democrats and Independents."

While saying he's "deeply impressed" with Sanders, he argued that Clinton has the "tenacity and skill" to be the party's leader and has the best chance to "stop the dangerous candidacy of Donald Trump."

She is 71 delegates shy of the number needed to claim the nomination, according to a tally by the Associated Press, and she's all but certain to cross the threshold when California and five other states hold contests on June 7. But losing the state, which she won in 2008, would complicate her efforts to unify the party.

California polls have indicated that the race between Clinton and Sanders is very fluid, with the former secretary of state's advantage ranging from 18 percentage points to 2 points. The endorsement by Brown carries weight: He has a 74 percent approval rating with California Democrats, and a 55 percent approval rating overall in the Golden State, according to a California Field Poll released in April.

Brown, a Democratic superdelegate to the party convention, met with Clinton's husband, former President Bill Clinton, recently at the governor's residence to discuss the 2016 election, the Los Angeles Times reported last week. Brown and Bill Clinton fought an acrimonious presidential primary battle in 1992. In his statement Tuesday, the governor said that the issues he raised in that campaign were similar to Sanders' emphasis on income inequality.

But he said it's time for Democrats to unify behind Clinton. Brown assailed presumptive Republican nominee Trump for having called climate change a "hoax," vowing to deport millions of undocumented immigrants, expressing openness to some countries building a nuclear bomb, and for his suggested Supreme Court nominees.

"The stakes couldn't be higher," Brown said. "This is no time for Democrats to keep fighting each other. The general election has already begun. Hillary Clinton, with her long experience, especially as secretary of state, has a firm grasp of the issues and will be prepared to lead our country on day one."