AFAIK, the Arizona primaries are open to all registered voters, and yes, the Democrats are McCain's strongest support base.
I was just thinking about what a betrayer McCain is. McCain makes deals with the Democrats, when the Democrats want to pass a controversial bill they will go to McCain and the other rinos to give them cover. This way they can deceive the people into believing that it was a bipartisan bill thereby keeping the people confused and feeling that no matter what party they vote for it won't make a difference. It just struck me as to how cynical this is, how it cheats the voters out of a real choice. McCain is part of this cynical deal-making that really treats the people with contempt. These manipulations and deceptions steals our power, they are treating us as if we are the enemy that must be defeated at all cost. It really is them versus us. The more I think about it, the more it fills me with disgust.