The Polarization of American Environmental Policy: A Regression Discontinuity Analysis of Senate and House Votes, 1971-2013

The partisan polarization of environmental policy is an important development in American politics, but it remains unclear how much such polarization reflects voter preferences, as opposed to disagreements between partisan elites. We conduct a regression discontinuity analysis of all major environmental and energy votes in the Senate and the House, 1971-2013. In total, we have 368,974 individual roll call votes by senators and House Representatives. The causal effect of electing a Democrat instead of a Republican in close elections on pro-environmental voting is large: when a Democrat wins, pro-environmental voting increases by over 40 percentage points. Because of the quasi-experimental research design, this difference cannot be attributed to the median voter's preferences. Next, we test hypotheses concerning possible explanations for the elite partisan conflict. The Democrat-Republican gap is the widest when fossil fuel interests make contributions exclusively to Republicans and when state-level public opinion is polarized.