California Gov. Jerry Brown endorses Clinton
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California Gov. Jerry Brown has endorsed Hillary ClintonHillary Diane Rodham ClintonCollins walks impeachment tightrope Hill.TV's Saagar Enjeti rips Sanders for 'inability to actually fight with bad actors' in party Hill.TV's Krystal Ball knocks Clinton's 'mean girl' comments against Sanders MORE for president ahead of next week's California primary, giving the Democratic front-runner a major ally as the race tightens.

Brown announced the endorsement Tuesday morning in a letter posted online, in which he called Clinton the only person who could beat presumptive GOP presidential nominee Donald TrumpDonald John TrumpMnuchin knocks Greta Thunberg's activism: Study economics and then 'come back' to us The Hill's Morning Report - House prosecutes Trump as 'lawless,' 'corrupt' What to watch for on Day 3 of Senate impeachment trial MORE


"Hillary Clinton has convincingly made the case that she knows how to get things done and has the tenacity and skill to advance the Democratic agenda," Brown wrote.

"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."

Brown praised Democratic candidate Bernie SandersBernie SandersThe Hill's Morning Report - House prosecutes Trump as 'lawless,' 'corrupt' Tensions between McConnell and Schumer run high as trial gains momentum Sanders wants one-on-one fight with Biden MORE’s campaign, adding that his populist message mirrored Brown’s 1992 presidential bid. 

But he noted Clinton's strong lead in both total votes cast and delegates won. 

"Clinton’s lead is insurmountable and Democrats have shown – by millions of votes – that they want her as their nominee," he said.

Brown said the stakes of the election couldn't be higher because of Trump's controversial stances. 

"This is no time for Democrats to keep fighting each other. The general election has already begun."

The Clintons have a tumultuous past with Brown, who ran against Bill ClintonWilliam (Bill) Jefferson ClintonTensions between McConnell and Schumer run high as trial gains momentum Nadler gets under GOP's skin 'Emotion' from Trump's legal team wins presidential plaudits MORE for the Democratic presidential nomination in 1992. The governor bashed Clinton as the "prince of sleaze" during that primary. 

And after Brown needled Hillary Clinton on the debate stage during that primary, Bill Clinton came to his wife's defense, declaring, "You're not worth being on the same platform as my wife."

Sanders has focused his campaign almost entirely on California’s June 7 primary, raising the stakes in the state. He is trying to give Clinton an embarrassing loss in the state with the largest amount of delegates.

Clinton will almost assuredly lock up the nomination regardless of the margin in California — she needs just 73 more delegates, according to The Associated Press. 

California alone awards 475, while primaries in five states also on June 7 award another 219. 

But a loss in the Golden State would be a tough pill to swallow for the Clinton campaign and could embolden Sanders supporters to make a strong push during this summer's Democratic National Convention for their candidate or his message. 

Clinton leads Sanders by 8 percentage points in California, according to a RealClearPolitics average of recent polls. But polls have varied wildly, with some showing Sanders within 2 points and others showing Clinton with a lead of 19 points.

— Updated at 9:49 a.m.