The campaign doesn't call people outside of their base because it is extremely hard to convince people to change their mind. There are a lot of popular articles

The campaign doesn't call people outside of their base because it is extremely hard to convince people to change their mind. There are a lot of popular articles dedicated to this topic recently if you Google some variants of "difficult to change people's mind" [1]. The vast majority of people have a consistent voting behavior, i.e. voting Republican / Democrat all their lives. I know of these stylized facts because I'm a political scientist who talks shop with my colleagues frequently. Regrettably I can't recommend a good book, but hopefully this answers your particular question. [1]: https://www.psychologytoday.com/blog/how-risky-is-it-really/201007/why-changing-somebody-s-mind-or-yours-is-hard-do https://www.psychologytoday.com/blog/how-risky-is-it-really/...