Matt Yglesias says that, as a philosopher, Derek Parfit would (should?) prefer Barack Obama. In Matt’s view Obama as President means a smaller chance of existential catastrophe and Parfit is especially concerned (correctly, in my view) with preventing such catastrophes. It’s also worth pointing out that Parfit is not such a committed egalitarian. In his view inequality across different time slices of your life is in principle as bad as inequality across different persons; on the self he is a Humean nominalist so what’s "a person" anyway? (Has not voter registration in Chicago mastered this perspective some time ago?) So we should worry more about the temporarily suffering and less about the poor, at least insofar as we are driven by egalitarian intuitions.
It always struck me as an awkward question for egalitarians whether the dying elderly — arguably the poorest people of them all, adjusting for human capital valuations — should be first in line for claims upon resources. You might argue that the dying elderly had lots of fun in the past, maybe so, but we don’t refuse to help out the high-time preference poor on these grounds so why should life history diminish the claims of the elderly?
I don’t wish to speak for Parfit but having spent two days in a room with him and Richard Epstein, I can say that a Parfit endorsement of McCain would very much surprise me, existential risk or not.