I have always considered Colin Powell to be only nominally a Republican (and of convenience at that), and thought as much even during the Gulf War and his SoS days. Deep down, I think he is actually nothing more or less than a "Colinpowell-ican" or a "Colinpowell-ocrat" depending on who is able to further Colin Powell's ambitions at any given time.
Mr. niteowl77
IMO Colin Powell ad for Obama was the most effective as for either campaign, easily.