American Politics Has Always Been Partisan; American Policy Not so Much...
Note to Self: My take was always that American politics was partisan but that American policy was not: that they were always enough people in the middle open to technocrat arguments to make the Hamiltonian Madisonian machine broadly work.
But when that vital center disappears.... When party discipline becomes strong because the people in the center believe they have to mobilize their base by toeing the party line....
Well, then you are reduced to a vain Downsian hope that people can assess and remember whose policies worked and whose policies failed...