The trouble with talking to people who are too interested in politics that relate to quantitative matters is that they don't seem especially interested in the quantitative matters. They see "politically realistic" as a constraint. They don't see "adequate to the circumstances" as especially relevant.
But political realism is a grossly premature calculation in the absence of quantitative reasoning.
The anecdote I like to repeat (I saw it in a comment somewhere by a "Z" (Zeke?) ) is of a fish viability study in Atlantic Canada. The scientists said the fish catch had to drop to X. The fishermen said they could not afford for it to go below Y. The Government, good liberals at the time, presumably, settled on the obvious (X + Y)/2 but (X + Y) /2 is substantially higher than X, so the fish population collapsed and now the fisherman have (another) Z which in this case stands for zilch.
First you have to figure out what is necessary. Then you come up with a bunch of schemes that achieve the necessary goals, with their various drawbacks and advantages, which, like it or not, will not work out to equal utility for each stakeholding constituency (in our case, that is everybody now living and, in a more diluted way but still significantly, everybody who might ever live).
You are as always entitled to your opinion, but you are not entitled to weigh in on this until you have a clear enough understanding of what is actually necessary.
If you feel that there is a responsible array of opinion on the matter of what is necessary, you should weigh your strategy appropriately to your degree of confidence in each possibility. This is even harder.
Once that is established, you figure out the politics. Maybe the market will handle it. Maybe not. List the scenarios out and come up with reasonable risk estimates. Then figure out what politics is necessary.
The reason the new Republicanism is irresponsible (both on climate and on budgetary matters) is because they have not taken into account informed and plausible scenarios of what is necessary. What they are doing is not conservatism. Neither conservatives nor liberals should mistake this for conservatism.
The reason the compulsive middle in America is irresponsible appears to be that they always were, but it wasn't clear until one of the official poles of debate went bonkers. They just split the difference. Either side of the matter is always "unrealistic". The solution is always "compromise".
Under circumstances with two moderate parties this works well enough and the middle looks smart. Those circumstances are gone, and now it turns out that many of them weren't very smart after all.
P.S. It begins to appear that Obama is of that school, but I'm not sure yet.