And so there's zero confusion on his threat:

Alabama Governor and white supremacist (”segregation, now, segregation tomorrow, segregation forever!”) George Wallace also used the phrase during his 1968 presidential campaign:

All of this, plus Jacob Frey is Jewish, so when Trump says “very weak radical left mayor” that is absolutely an antisemitc dog whistle to the alt-right. He’s basically reinforcing the white supremacist belief that Jews are evil puppet masters who control all other minorities (especially Black and Brown people) in a bid to take down the white race. This is literally word for word a thinly veiled regurgitation of key white supremacist tenets. He’s 100% signalling that he’s ready to start a race war.