Sadly, politicians do use studies, polls and legal precedents, but they start with the vision of the kind of society they want and pick and choose which studies

Sadly, politicians do use studies, polls and legal precedents, but they start with the vision of the kind of society they want and pick and choose which studies, polls and legal precedents give them cover for the policies they are pushing. Partisanship has made this far worse since politicians aren't even forced to reckon with contradicting studies, polls and legal precedents because they can just dismiss those that contradict their vision as the work of competing partisans.