Booker is a perfect hybrid between the oration skills of Barack Obama and the (perceived) crookedness/shadiness of Hillary Clinton. He's probably the single worst candidate that the Democrats could realistically nominate in 2020, and the only one who could put places like Maine AL and Minnesota firmly in the Trump column.
This. Literally nobody likes him except for Democrats, who also found Her Majesty inspiring and were shocked when she lost Middle America.
I think Cory Booker is probably the only candidate whose name I have seen bandied around seriously that will absolutely lose to Drumpf in 2020. But the consultants and donors running the party are apparently dtf us all into a climate-change induced grave so I wouldn't rule out his candidacy yet.