"Climate change is not a hoax."
Forget all the policy, and the economics, and everything else: those are details. At the core of everything is process; details are merely a product of process. Science, for example, is a process for generating facts/details; theology, ideology, and pulling things out of your ass are other processes.
And in that one statement, in the mere fact that Obama had to even issue the statement, it is revealed in stark clarity that one political party chooses science as a process, and one does not.
Regardless of your position on any other issue, this single fact alone compels rational voters to one and only one choice.
(I feel compelled by fairness to point out that this did not use to be true; that the Republican party has a long tradition of hard-nosed rationality while the Democrats were into moonbeams and unicorns; but things have changed.)