He says it's not about race, and I find it very easy to believe him. From a policy standpoint, Colin Powell has always been of the Schwarzenegger/Giuliani mold--i.e. liberal on social issues--and that came through loud and clear as he explained himself:
As a key reason, Powell said: "I would have difficulty with two more conservative appointments to the Supreme Court, but that's what we'd be looking at in a McCain administration."
That's the long and short of it right there.