One of the most important rules in partisan politics is this: when your opponents are fighting amongst themselves, stay out of it. House Democrats spent the last few days in a civil war over whether Nancy Pelosi and the Congressional Black Caucus are racists or whether the “Freshman Squad” are idiots. It’s a once-in-a-lifetime apotheosis of that axiom, a singular and historic opportunity to let the party of identity politics shred itself to pieces over it.

That is, unless a Republican interrupts it and gives both sides a new target. Enter Donald Trump:

Ahem. As Taylor Millard noted yesterday, only one of the “Squad” foursome “came from” somewhere else — Ilhan Omar, a refugee from Somalia. The other three “came from” the Bronx (Alexandria Ocasio-Cortez), Detroit (Rashida Tlaib), and Chicago Cincinnati (Ayanna Pressley, relatively speaking the quietest of the four). Last I looked, all of those places are in the same country … ours.

Even if all four were naturalized citizens, though, go back to where you came from is an ugly response to criticism coming from the American head of state. That’s not to say it doesn’t have its appeal in certain quarters — I can still remember the “America — Love It or Leave It” bumper stickers from the Vietnam era — but it’s an appeal to base instincts of exclusion rather than a reasoned response. In this case, their recent insanity didn’t even require any response, as none of it was aimed at Trump but at their own party leadership.

Donald Trump might have plenty of defenders on this point just the same. “America Love It or Leave It” still has a lot of curb appeal regardless of its merits or its particular application in this instance to people of color. What’s difficult to argue is that Trump’s attack will end up benefiting Democrats, especially the “Squad,” by being a rallying point for Democrats at a point in time where they desperately needed a common enemy to halt their internecine warfare. John Hinderaker, normally a huge fan of Donald Trump, is aghast at the strategic error, calling it “the single stupidest act of Trump’s presidency”:

Regular readers know that I am a fan of President Trump, and more often than not, a fan of his use of social media. But today he committed the worst unforced error of his presidency, one that we will hear about from the Democrats from now until November 2020. …

The Democrats have been self-destructing, with the progressives denouncing Nancy Pelosi and other members of the party’s leadership as racists. That conflict has dominated the news, and I am sure Trump is right that Nancy Pelosi would be happy to work out travel arrangements to get rid of the Squad. But now she won’t have to. Trump’s attack on the Squad was so foolish that I would assume it to be a case of drunk-tweeting, except that the President doesn’t drink.

Sure enough, the headlines yesterday and today have both sides of the civil war turning their guns on Trump:

Pelosi denounced Trump’s tweets as “xenophobic comments meant to divide our nation,” while the four congresswomen promised to continue fighting Trump’s agenda and accused him of trying to appeal to white nationalists.

Trump’s remark swiftly united a House Democratic caucus that had been torn apart in recent days by infighting between Pelosi and the four freshman women of color — Democratic Reps. Ayanna Pressley (Mass.), Rashida Tlaib (Mich.), Alexandria Ocasio-Cortez (N.Y.) and Ilhan Omar (Minn.). It also comes after Trump announced that U.S. Immigration and Customs Enforcement officers were preparing to round up migrant families that have received deportation orders across the country. …

Within a few hours on Sunday, Democratic lawmakers were united in defending their colleagues against Trump’s attack.

“I’ve been trying to figure out how to bring everybody together — I think the president just did that for us,” Rep. Debbie Dingell (D-Mich.) said. “Nobody in our caucus is going to tolerate that kind of hatred.” …

“Trump is now turning the same birtherism he directed at President Obama against women of color serving in Congress,” Rep. Don Beyer (D-Va.) said in a tweet. “Everyone should call this what it is: racism.”

And so on. We can expect much more of this over the next sixteen months, none of it prompted by any necessity for Trump to get involved in the first place.

Is it fatal? Naah. Lots of people made it their living to proclaim specific events as “the end of Trump,” and this misstep isn’t even close to the potential gravity of the Access Hollywood tape. If Mick Mulvaney can prevail on Trump to stay out of this Democratic civil war, this incident may only end up being a blip. Trump’s tweets didn’t resolve the conflicts between the “Squad” and party leadership — they only distracted from it momentarily. That fight will erupt again, and likely sooner than later, as the corrosive nature of identity politics will eventually eat its Dr. Frankenstein.

That is, Dems will finally have the identity-politics meltdown if the GOP townspeople and their pitchforks and torches stay out of the way. Someone give the president a “harrumph,” and a boatload of popcorn to pass in place of his smartphone.

Update: Per Pressley’s House page, she was raised in Chicago but born in Cincinnati. I’ve corrected it above.