There's an old French saying, attributed to Antoine Boulay, that goes, "It was worse than a crime; it was a blunder." That's my initial thought hearing that Trump officials used an unsecured service (Signal) and shared attack plans with a journalist. But I suspect this blunder will stick around a while, and really hurt the Trump administration in a way many scandals and crimes haven't.
Trump learned a lesson a long time ago- if you have one scandal, people focus on it. If you have a dozen, it becomes background noise, and people tune out. (Bill Clinton also mastered this lesson). So most scandals that you would expect would have sunk Trump never seem to stick to him.
But I think this one will, unless Trump takes decisive action quickly. People form opinions about politicians (and really, any public figures). Those opinions get hardened over time into their reputations. Scandals and Crimes that fit in with those reputations don't matter- people are expecting them.
So Trump could sleep with a porn star and pay her off to be quiet, and it doesn't matter. We (the public) expect Donald Trump to do that. When he acts like an ass, we shrug; Trump has always been a vulgar ass. That's part of his package- no one is surprised when he acts that way.
But he's also supposed to have built a reputation as a guy who doesn't tolerate failure. Hell, his catchphrase was "You're Fired". When underlings screw up, Trump is supposed to can them, quickly. That's his reputation as well.
So there's two choices here:
Trump can act quickly, firing people who allowed this to happen (the obvious scalp is Mike Waltz, who accidentally invited Jeff Goldberg to the chat). That is in line with Trump's reputation, and if that happens, this will go away like every other scandal.
But if Trump doesn't, the public will notice. Now, keeping loyal people who botch things is allowed for most Presidents. But that's not Trump's reputation. It will look bad, and he has enough problems already. At some point, the decline in popularity becomes too difficult to climb out of. And while Trump is President for four years, the people have votes even this year to swap over the House.
