The more horrible Republicans become, the farther to the right Democrats can move while still claiming moral superiority in comparison and defending their donors from attacks from their left flank. Most divisive issues in the US have been benefits other countries have had for so long that they are now just assumed, but Americans don't travel and simply ignore such obvious evidence even if it is brought to their attention.

Until we can force a third (or more) party into the mix this will always be the nature of American politics. In any other modern society in the world our Democratic party would be extremist conservatives. The reason Republican anti-democratic measures in the states get so little pushback from Dems is that they are also protected from "the will of the people" in the form of third parties.