The classic solution to this problem is to find a common enemy against whom all the disparate factions can unite.
Hmm, I wonder who that might turn out to be?
Yes, but that didn’t work in 2016. Blacks and homosexuals weren’t afraid of Trump; the former in particular helped elect him by refusing to support Hillary. Now the people left out are very vocal (see Bernie and Jill Stein supporters); the left isn’t a homogenous bloc.