With Democrats increasingly attacking each other with a vitriol they once reserved for President Trump, an anecdote involving President Lyndon Johnson fits the moment. As recounted in the riveting memoir of Joseph Califano, Johnson’s top domestic adviser, the president was meeting with civil rights leaders in the hot racial summer of 1967.

Dems were sharply divided over several issues, including how to respond to riots in Detroit and Newark, and LBJ hoped to corral NAACP leader Roy Wilkins and Urban League executive director Whitney Young into his corner.

At a White House meeting, Johnson recited his Great Society accomplishments, but Wilkins and Young appeared numb and in despair, saying they couldn’t control the young rioters, Califano writes in “The Tragedy and Triumph of Lyndon Johnson.”

It was then that Johnson attacked the left wing of his own party. “A liberal is intolerant of other views. He wants to control your thoughts and actions,” Johnson declared. Califano then describes the president moving forward in his chair to deliver his punch line. “You know the difference between cannibals and liberals? Cannibals eat only their enemies.”

Five decades later, only the labels have changed.

Liberals are no longer liberals, they are progressives or social justice warriors or anti-Trumpers. Whatever they call themselves, they are still eating their friends as well as their enemies.

Munch, munch.

The bloodletting starts at the top, with the 2020 presidential candidates. In their very first debate, Sen. Kamala Harris shredded front-runner Joe Biden in a planned attack over school busing issues dating back to the 1970s.

Her message, delivered with contempt, was highly personal and contained no relevant policy distinction. Yet it was successful among left-wing voters, according to polls showing Harris surging after the debate while Biden’s support dropped.

Speaker Nancy Pelosi is constantly being undercut by House Dems who want to impeach Trump yesterday, making her look weak and leading her to make wild accusations of criminal conduct against Trump to prove she also hates the president of the United States.

Others in her caucus, especially rookie Alexandria Ocasio-Cortez, are pushing Pelosi to the left with their nutty Green New Deal, which would destroy the economy if enacted. And the two Muslim women in Congress, Ilhan Omar and Rashida Tlaib, keep infuriating many of their fellow Dems with their obvious hatred of Israel.

Deep blue New York is not immune from the civil war between the far left and the far far left, with accusations involving race and gender, a mainstay in attacks on Republicans, now being hurled at Dems. Each time Gov. Andrew Cuomo criticizes Andrea Stewart-Cousins, the black leader of the state Senate, her defenders respond by accusing Cuomo of treating her differently than he treated her white male ­Republican predecessor.

No evidence was needed. Stewart-Cousins is a black woman, so Cuomo, a white male, must be guilty.

Then there is the extraordinary Dem-vs.-Dem slugfest over the disputed primary for Queens district attorney. Supporters of the insurgent candidate sounded like so many bitter Hillary Clintons when they said the election was stolen — except they were making the charge against their own party’s ­establishment!

The insurgent, Tiffany Cabán, a political newcomer, declared victory on Election Night, and her upset seemed to confirm that last year’s victory by Ocasio-Cortez, who had endorsed Cabán, was no fluke and that insurgents really were taking over the New York party.

Then, suddenly, a count of paper ballots gave the Queens establishment pick, Melinda Katz, a lead of just 20 votes.

As the fight headed for the courts, AOC suggested foul play , tweeting, “This is pretty wild, and a testament to why everyday people in NYC have begun to vote out those engaged with Tammany Hall-style political machinery in the first place.”

Another Cabán supporter, new state Sen. Alessandra Biaggi, tweeted sarcastically: “Here’s something we ALL learn where we are two years old — people of INTEGRITY don’t need to steal Bc STEALING elections is definitely the sign of a real leader…how dumb do they think we/the people are?”

A party out of power often tears itself apart as factions scramble for control, as Republicans did in 2016 over Trump’s candidacy. Some in Congress still hold their nose when they support him.

But the president’s popularity with rank-and-file Republicans — his approval hovers between 80 and 90 percent — instills discipline and dishes out punishment to those who stray too often.

Jeff Flake of Arizona and Bob Corker of Tennessee are former senators largely because they sniped at Trump too much. Rep. Justin Amash, who called for Trump to be impeached, quit the GOP last week, with the president gleefully greeting the decision as “great news.”

Dems, of course, could also pull themselves together and unite behind their nominee for 2020. But even allowing for how much they want to defeat Trump, it’s more likely their savage attacks on each other will get bloodier and cost them the election.

For one thing, there is no strong Trump-like personality capable of dominating the party and turning it to a more sensible policy course. And recall that Clinton and Bernie Sanders never reconciled before the 2016 general election and there is still bad blood between them.

As for LBJ, his cannibal line proved prophetic. Sen. Eugene McCarthy, running against the Vietnam War, nearly upset Johnson in the 1968 New Hampshire primary, and the president, realizing he had lost his party, shocked the nation by announcing he would not seek re-election. In the fall, Richard Nixon was elected president.

Munch, munch.

Can’t stand success

Given their obsession with race, you might assume New York’s mayor and schools chancellor would celebrate the fact that all 53 eighth-graders at a Bronx middle school aced the state’s algebra exam. But you would be wrong because Mayor Bill de Blasio and Chancellor Richard Carranza were silent.

The reason: The high-scoring kids attend a charter school, Success Academy 2 in Concourse Village, and their sensational achievement shames most other public schools in the district and city. And with nearly all 53 of the high scorers nonwhite, the kids put the lie to the claim by de Blasio and Carranza that racism prevents black and Hispanic kids from doing well on standardized tests.

In a better city, the students and their algebra teacher, Karina Mateo, would be feted at City Hall and educrats would be lining up to learn from her success.

Instead, crickets. Shame on the mayor and chancellor. Their silence convicts them of hypocrisy.

A no-win for Christians

My trip to Israel and Jordan was eye-opening in many good ways, and some not so good. One discouraging insight came in a conversation with a Palestinian Christian man.

Given that he is a member of a small and shrinking religious group in a nation dominated by Jews and Muslims — only 2 percent of Israelis identify as Christians — I asked if he often felt like the odd man out.

His reply was haunting. “The Israelis see us as Arabs, and thus the enemy,” he said. “The Palestinians see us as Christians, and thus as infidels.”