No issue better reflects the growing chasm between America’s two political parties than that of the environment, which was born in the Republican Party and was once a broadly bipartisan issue. The 1972 Clean Water Act, for example, passed the Senate, 86-0, and the House, 366-11 – and then easily overrode Richard Nixon’s veto, 57-12 and 247-23. But the League of Conservation Voters’ latest National Environmental Scorecard tells a completely different story, particularly in the House of Representatives, where most Democrats score above 90%, most Republicans below 10%. Among the leadership the difference is even starker – with Democrats at 92% and Republicans at 2%. And there’s a nice consistency among the declared presidential candidates: Cruz 0%; Paul 0%; Rubio 0%. The partisan differences are escalating for two reasons: (1) most Republicans’ current scores are significantly lower than their lifetime averages (Oregon’s Greg Walden has dropped from 11% to 3%, for example, and Virginia’s Frank Wolf from 26% to 6%); and (2) the tea party wing is pushing the GOP deeper into anti-environmental territory. Many House votes now attempt to roll back existing protections – keeping pesticides out of our waterways, for example, and carbon pollutants out of the air. Others seek to prevent the Defense Department from replacing fossil fuels with biofuels and the EPA from using peer-reviewed scientific studies with confidential health information.

This creates a dilemma for the League, as it tries to maintain a semblance of non-partisanship, something it has traditionally done by supporting Republicans with mediocre records – like Maine’s Susan Collins (55%) – over pro-environment Democrats. Such Republicans are ever harder to find.