Do you mean Trump with his red scare ?
From what I have seen Mamdani is no Communist. I would not even call him a socialist. A Democratic Socialist for sure, but that is not a socialist.
Trump just labels everyone to the left of the Austrian Corporal as commies. I don't even think he knows what a communist is. Then again, I don't really know what communism is, and I live in a Communist country. In fact, communists can't seem to agree what communism is. So they are stuck in an endless half way house called socialism, while they try to figure out what communism is. And the paradox is, I think, that they can't declare an actual communist state, because in communism there is no state.
And yeah.... I am about to be flamed :-)