Republican electoral victories Tuesday cast doubt over whether the US would enact any significant measures to curb planet-heating emissions in the near-term.
States were still tallying results on Wednesday as the Trump administration officially withdrew from the Paris climate agreement.
According to HuffPost, that makes the US the only country to exit the nonbinding global pact to cut climate-changing carbon emissions.
In Montana and Texas, climate-change-denying candidates cruised to victory.
While many Senate and House races remain undecided, two sunny spots for climate advocates and environmentalists were in Arizona and in Colorado.
Democrat Mark Kelly handily beat Arizona Republican Sen. Martha McSally. Kelly made tackling climate change a key part of his platform.
And in Colorado, former governor and 2020 presidential contender John Hickenlooper ousted Republican Sen. Cory Gardner.
Claiming to be a 'national leader' on climate, Gardner consistently peddles the conspiracy theory that environmentalists are plotting to control the economy.