This wasn't just some random racist tweet. This is actually one of Trumps far more calculated attacks. I say it a lot round here (and get called a "nazi sympathiser" or "woke independent" a lot for saying it) but if you just think of Trump as just a racist idiot who got lucky, then you're seriously underestimating him.
It's no secrect that the democrats have been eating themselves a bit of late. The far "progressive" side of the democrats seem to be emulating the British Labour party who basically began purging any moderate MPs and anyone who would disagree with their leader on any issue. The Justice Democrats are even trying to oust African American and hispanic lawmakers for not being progressive enough. Them calling out Pelosi as a racist and trying to drive out the moderates is a terrible idea if they want to stay elecatable.
Trump coming to Pelosi's defence is clearly going to give her more problems from the progressives, and make them double-down on their criticism of her. Trump as a character witness is the last thing ANYONE wants.
And then you get to his latest tweets. Sure it's clearly racist but he specifically doesn't mention people by name, and so it's down to the democrats to decide that he was referencing all 4 of the squad specifically. All the media are saying it's directed at those four but he doesn't call them by name - He's vague enough to be able to claim plausible deniability and argue that he was just speaking in general terms... albeit directed at Ilhan Omar, but I'd wager far more people are sympathetic to his views on her than they let on.
Lets make this clear; this won't effect anyone who was going to vote for Trump already anyway. IT likely won't effect anyone on the fence on Trump. It will be a nice rallying cry for Democrats to come together - BUT it's for them to come together around the far-left squad, who are still enveloped in the identity politics that everyone else is trying to get away from. He's forcing them to their extreme end as, if the Democrats ostracise Pelosi supporters and any moderate ground they're fucked.
No matter how much people in the UK HATE the Tories, a lot couldn't bring themselves to vote for Corbyn. It could prove the same in the US - No matter how much they hate Trump, they might get very nervous about voting for the Democrats if they get dragged towards their extremes, especially if stunts like this just radicalise the furthest on the left even more.