Republicans would never nominate McCain or a Black Guy for President. They have had their chance to do both and win big in 1996 and 2000 and passed it up.
If common sense was present in the Republican Party, I would be supporting the party and there would be no need for the Democratic Party.
Don't be so certain. Powell had no interest in being president; he stated that on a lot of occasions, and I've got no reason to think that he really felt otherwise and was just being "held down by the man". Don't forget that Republicans are a big-tent party, now. The war on terror made a lot of people turn into hawks, regardless of their views on things like gays and abortions.
And please don't try to turn this into a racial thing. Democrats have also had their chances to nominate a black man and haven't done so, even though they claim to be the party of minorities.