You assume they'll lose in 2020. It could very well be 8 years (or 12).

No one thought GWB would be a 2-term president. No one thought Trump was electable.

Thinking the assault on the EPA will suddenly be reversed next election - that's fantasy thinking.

Fact is, the government should be meaningfully increasing our regulation of emissions and pollution (in terms of costs) or some will cause irreversible results in the global ecology (coral reefs, ocean acidification, carbon levels, global temperature). Not moving forward means we lose ground.