John McCain was plenty centrist until Obama emerged as a Democratic equivalent, at which point the media couldn't seem to accept two centrists running against each other from opposing parties. So repainting began, and McCain was portrayed as just another right-wing frother. Still, it's undeniable that non-centrists in both parties made it exceedingly difficult for Obama or McCain to remain centrist. In short, their own far-left and far-right supporters. They know who they are.