To enact major policy change in the USA generally it is imperative to either have 75% support from the public or significant support in both the Democratic and Republican parties. An exception like health care reform in the last Congress when nothing close to 75% of the public and virtually no Republicans supported the changes that became law prove the general rule.
On global warming 65% of the public believes global warming is real and caused by humans pumping heat trapping gas into the atmosphere and raising the concentration of that gas from 280ppm to 393ppm over the last 150 years. That's an impressive number but not enough support to overcome well-financed attacks, especially since the Republican party today largely outright denies global warming is real.
One united party can gridlock the US Senate, given the ubiqitous use of the filibuster by the Minority Leader Senator McConnell from Kentucky in the last two Congresses, turning the Senate into a body where 60 votes are needed to enact most bills.
To change the political climate, the key population groups are not the 65% accepting climate science or the 17% that denies global warming is happening (see prior post about the AP/Ipsos poll). The pivotal segment of opinion is the 18% that say temperatures are rising but the cause is natural. This group should be the focus of education and outreach work.
If about half of that 18% moves to the camp that human activity is causing temperatures to rise, then two things happen. First, 75% of the public will then accept climate science and our democratic system generally responds when 75% of the public coalesces.
Then significant numbers of elected Republicans also will accept climate science. Why? The natural-warming group is heavily concentrated in the Republican Party.
Splintering the natural-warming group will move enough elected Republicans to change the political climate and is the key to global warming policy.