This past weekend, all the republican candidates were invited to a debate hosted by a historically black college Morgan State University. Four candidates could not make the debate. And, of course, it gave the candidates that were there plenty of ammo to say how Thompson, Guiliani, McCann, and Romney don't care about the minority vote.
Even though these candidates expressed well in advanced that they had scheduling conflicts, they were all lampooned.
As the time-horizon closes to the primaries, each and every candidate must do his best to raise the support needed to win the election. Being a minority myself, I can understand that Thompson, et al had scheduling conflicts that they couldn't change. Fund raising is crucial during this time.
Every special interest will want to have a debate concerning their political agenda. At this point, they simply cannot say yes to every invitation. In fact, one must learn to say no.
Perhaps the ability to say "no" is a good indicator as to who can be president.