Two political scientists suggest that the most powerful factor driving your partisan beliefs in the charged political landscape of the United States is fear - most notably, fear of the other side.
This is a pretty depressing conclusion, because it implies that not only are we failing to appeal to anything more elevated in our humanity than a simplistic reaction to real (or perceived) threat, but also that people of both sides of the political spectrum are easily manipulable through appeals to fear, which form a disturbingly large fraction of the shrill social media shares that are becoming a common means of gathering information about the world. We're beyond preaching to the choir; we're howling to the other torch bearers in the pitchfork-weilding horde.
Not you, of course, I'm sure you're entirely rational and right-thinking. Funny how everyone thinks that, even people whose world-views you would find odious. The trope of "everyone else is an idiot except me and my in-group" has become so common that I've begun to believe that it's also a powerful, manipulable state encouraged by those whose power is fed by partisan divisions. The more that you consider other people to be fools, the more fearful you are of the effects of their idiocy... and the more likely you are to stick to the ways of the people close to you, defending your shrinking piece of the turf from all comers.
Easy for me to say. I struggle with the same feelings. It's a stretch for me to be inclusive in my thinking, even though I work with (and fundamentally trust) many people whose belief systems seem alien, even corrosive.
When you seek consensus to manage a conflict, one of the first steps is to establish the many things you have in common with the other party. Sometimes in American politics, it feels as if we're living in entirely different worlds than our opponents. Is common ground shrinking? Or is no one looking for it any more?
Of course, if you're going to fight your opponent to the death, there's no need to seek consensus.