Dana Milbank: Is it any wonder Washington is broken? The friendship tree has died.

Washington • Metaphor alert! The friendship tree has died.

Fourteen months ago, President Trump and French President Emmanuel Macron stood on the South Lawn of the White House for the ceremonial planting of a young oak from France's Belleau Wood, where American soldiers fought in World War I.

"This oak tree (my gift to @realDonaldTrump) will be a reminder at the White House of these ties that bind us," Macron tweeted.

Or not. After the two leaders departed, U.S. officials dug up the tree and isolated it in quarantine — the arboricultural version of family separation — and there it died. French media broke the news this week of the demise of the “friendship tree” at a time when the once-promising Trump-Macron relationship has similarly withered.

A tree of friendship literally fails to take root at Trump's White House: Could there be a better allegory for this presidency?

There are serious differences of view in the United States today, and of culture and race. But that is not our real problem. The real problem is that with each new insult and outrage, each shattered norm, each move to dehumanize an opponent, we are breaking what Lincoln called the "bonds of affection." We are losing the goodwill that makes it possible to overcome differences.

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Last Tuesday, House Minority Leader Kevin McCarthy met privately with House Majority Leader Steny Hoyer and indicated he wouldn't oppose Democratic plans to enact the first congressional pay raise in 10 years. They agreed, Politico reported, that they would make sure their respective campaign arms would not attack each other over the pay raise.

A day later, the National Republican Congressional Committee, the campaign arm of House Republicans, issued a press release attacking Democrats for the pay raise, saying "these socialist elitists" want "middle-class taxpayers to give them a $4,500 pay raise!"

It's unclear whether McCarthy was dishonorable or just incompetent, but in any case, how can you negotiate with such a man? Eventually, the NRCC retracted its press release, but the damage was done. The pay raise — needed to help less affluent people run for Congress — was pulled from consideration.

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Trump strode onto the South Lawn at noon Tuesday, not far from where the friendship tree once stood. He had some thoughts to offer reporters before taking off for Iowa, where he would give a campaign speech.

Joe Biden, who planned to give a speech calling Trump an "existential threat" to the country, is "failing," Trump said. He's "even slower than he used to be." "He's the weakest mentally." Pointing to his forehead, Trump said: "Joe is the weakest up here." Furthermore, he said, "Joe Biden is a dummy."

Trump also offered his view that Nancy Pelosi is "a mess."

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Last week, while the NRCC was attacking Democrats for the pay raise their leadership agreed to, Senate Majority Leader Mitch McConnell gave an interview to radio host Guy Benson.

In it, he described Democrats as his "enemies," not his opponents. "I've kind of enjoyed playing off of my enemies," he said, adding that he calls himself the "Grim Reaper."

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House Democrats approved legislation Tuesday authorizing lawsuits that could force Attorney General William Barr and former White House counsel Donald McGahn to comply with congressional probes. The legislation itself was relatively tame — Democrats called off a full contempt vote — but that didn't stop apocalyptic language on both sides.

From Democrats: "Relentless campaign of obstruction and stonewalling"; "Make Richard Nixon look like an Eagle Scout"; "An autocratic king."

From Republicans: "Knee-jerk lawsuit"; "Blatantly partisan"; "Modern-day flat-earth movement"; "Fantasies!"

"Who does he think he is, a dictator?" Rep. Maxine Waters, D-Calif., said of Trump.

Rep. Jim McGovern, D-Mass., said Trump talks like a "mob boss."

The speaker pro tempore advised members, not for the first time, "to refrain from engaging in personalities towards the president."

McCarthy, fresh from his pay-raise stunt, countered that Democrats were acting "just because someone despises somebody else" and because "the election didn't turn out the way you desire." He alleged Democrats "break the law just because you lost an election."

Is it any wonder Washington is broken? The friendship tree has died.

Follow Dana Milbank on Twitter, @Milbank.