I'm a bit late to this party, but the Pew Research Center recently released a new report about changing views on evolution in the United States. The big takeaway was that a plurality of self-identified Republicans now believe that no evolution whatsoever has taken place since the day of creation - let alone that evolution is driven by natural selection.
The move is big: an 11-point decline since 2009. Obviously there isn't any new scientific evidence driving this rejection of Darwin. And Democrats are slightly more likely to believe in evolution now than they were four years ago. So what happened after 2009 that might be changing Republican views?
The answer is obvious, of course: the election of a Democratic president. Wait - is the theory of evolution somehow related to the Obama administration's policies? Not that I'm aware of, but that's not the point.
The point, instead, is that Republicans are being driven to identify in all ways with their tribe - and their tribal belief system is dominated by anti-science fundamentalists. For some time now it has been impossible to be a good Republican while believing in the reality of climate change; now it's impossible to be a good Republican while believing in evolution.
And, of course, the same thing is happening in economics. As recently as 2004, an annual Economic Report of the President published during a Republican administration could espouse a strongly Keynesian view, declaring the virtues of "aggressive monetary policy" to fight recessions, and making the case for discretionary fiscal policy, too. (Naturally, the only form of discretionary fiscal policy considered was tax cuts, but the logic was straight Keynesian, and could have been used to justify public works programs equally well.)
Oh, and the report from 2004 - presumably written by Greg Mankiw, then President George W. Bush's chairman of the Council of Economic Advisers - used the "s-word," calling for "short-term stimulus." Given that intellectual framework, the re-emergence of a 1930s-type economic situation, with prolonged shortfalls in aggregate demand, low inflation and interest rates at zero, should have made many Republicans more Keynesian than before.
Instead, we saw Republicans - the rank and file, of course, but economists as well - declare their fealty to various forms of supply-side economics. This has to be about tribalism. All the evidence, from the failure of inflation and interest rates to rise despite huge increases in the monetary base and large deficits, to the clear correlation between austerity and economic downturns, has pointed in a Keynesian direction, but Keynes-hatred (and hatred of other economists whose names begin with "K") has become a tribal marker, part of what you have to say to be a good Republican.