California Gov. Jerry Brown endorsed Hillary Clinton this morning in an "Open Letter to California Democrats and Independents," in which he says that a vote for Clinton "is the only path forward to win the presidency and stop the dangerous candidacy of Donald Trump."

In the letter Brown is highly complimentary toward Bernie Sanders and his campaign, and says he is "deeply impressed with how well Bernie Sanders has done." It also argues that, in a sense, Brown's own 1992 primary campaign offered a template for the sort of grassroots fundraising effort that Sanders has taken to a new level.

But Brown says that 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." And that currently her "lead is insurmountable and Democrats have shown — by millions of votes — that they want her as their nominee."

Consequently, he thinks it's time for the party to come together:

But there is more at stake than mere numbers. The Republican nominee, Donald Trump, has called climate change a "hoax" and said he will tear up the Paris Climate Agreement. He has promised to deport millions of immigrants and ominously suggested that other countries may need the nuclear bomb. He has also pledged to pack the Supreme Court with only those who please the extreme right. The stakes couldn’t be higher. Our country faces an existential threat from climate change and the spread of nuclear weapons. A new cold war is on the horizon. 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.

Jerry Brown's decades-long rivalry with the Clintons

To most people, the news that a prominent incumbent elected official is backing Clinton will come as no surprise — she is the overwhelming choice of the Democratic Party establishment and has consistently outmatched Sanders in endorsements.

The Brown endorsement is notable largely because of the extensive personal animosity between Brown and the Clinton family. This is Brown's second go-round as governor of California, an office he also held from 1975 to 1983 while Bill Clinton was governor of Arkansas. Clinton and Brown ran against each other for the 1992 presidential nomination, and things got pretty heated.

To see how heated, take a look at this exchange between Bill Clinton and Jerry Brown in a 1992 debate. It starts with a softball lobbed at Brown about Clinton's electability that Brown turns into a vicious attack based on a now-forgotten scandal involving conflicts of interest in Hillary Clinton's legal work.

"He is funneling money to his wife's law firm," Brown says. "It's not only corruption, it's an environmental disaster, and it's the kind of conflict of interest that is incompatible with the kind of public servant we expect for president of the United States." Brown goes on to say he would refuse to serve as Clinton's vice president. (This argument was somehow literally about chicken shit.)

Clinton's response: "I feel sorry for Jerry Brown." They go back and forth, with Clinton calling Brown dishonest and counterpunching with: "Jerry comes here with his family money and his $1,500 suit and his lying attacks."

Really. Watch it. It's amazing.

Brown lost the primaries decisively but took his fight all the way to the convention. He never endorsed Clinton in '92, and his delegates occasionally interrupted the nominating proceedings with chants of, "Let Jerry speak!"

There's been some talk of Sanders mounting a similarly disruptive post-campaign, and Brown's endorsement is significant primarily as a warning shot against imitating his own behavior from 25 years ago.