Cutting taxes is the opposite spectrum of the economic theory. It is based in Says law where supply determines demand. The problem with Republicans since Nixon (especially Reagan) is that they never managed to get it into their heads that increased military spending coupled with deregulation and cutting of corporate and income taxes amounts to a disaster. Nothing Keynesian about it. I think you are getting too attached to Krugman's interpretation of "government intervention" which he twists and turns in order for it to fit his agenda. The link between cutting taxes "the modern Republican way" and Keynesianism is tenuous at best.