imo because he has polarised all voters except his core base. So, in key states he is still easily winning the vote of whites, men, 45-64, evangelicals, no college degree (albeit by smaller margins than he won these in 2016 imo). In some states he has still maintained the over 65s, but in others there appears to be a shift away from him. Other segments like women, african americans, under 35s, latinos are moving further away from him imo. So, he has spread himself too thin with a focus on his core base but is unable to gain votes from the other segments. If his core base has shrunk by a small margin he won't be able to win the key battleground states imo. That's now, let's see how things look in November.
