To take the religion + politics thing further, consider that the president is hailed as being sent by God, and is surrounded by Christian Dominionists that are actively trying to apply make the U.S. a theocracy.
That's bound to stir up some passion on both sides, being that the stakes are rather high.
I also think politics (I'm not sure if it has always been that way, but I don't remember it like this when I was younger) has a lot of parallels to religion and that similarity is growing. I do actually believe this is rooted in the growing partisanship. That political answers are not "best solution vs a different solution" but "good vs evil". Partisanism relies on good vs evil. There's a John Cleese skit about extremism that always makes me laugh[0].
[0] https://www.youtube.com/watch?v=wXCkxlqFd90