Author John Daniel Davidson profileThe theological fault lines that divide America’s 50 million or so Catholics from its roughly 130 million Protestants have been largely set aside when it comes to politics in the Trump era, if only because most practicing Christians in the United States understand they have a common foe in the secular left. When Democrats are openly trying to drive all forms of Christian piety from the public square and impose what amounts to a neopagan morality, it tends to focus one’s attention on the near enemy.

But not this week. President Trump’s diatribe against Pope Leo over the weekend and the ensuing fallout triggered an online fracas between Catholics and Protestants that exposed those fault lines and called into question the durability of the conservative coalition that has twice sent Trump to the White House. …