Tribalism is now not just one force in American politics, it's the overwhelming one, and tribalism abhors reality if it impugns the tribe. But you can't have both tribalism and public health. When you turn wearing a simple face mask into a political and cultural symbol of leftism, when you view social distancing as a concession to your enemies, you deeply undermine the power of millions of small impediments to viral outbreak.
What we are seeing is whether this tribalism can be sustained even when it costs tens of thousands of lives, even when it means exposing yourself to a deadly virus, even when it is literally more important than your own life. We are entering the Jonestown phase of the Trump cult this summer. It is not going to be pretty.