RT Article T1 From backwaters to major policymakers: Policy polarization in the United States, 1970-2014 JF Perspectives on politics VO 16 IS 2 SP 416 OP 435 A1 Grumbach, Jacob 1987- LA English YR 2018 UL https://krimdok.uni-tuebingen.de/Record/1912562545 DO 10.1017/S153759271700425X