Republican senators won't attend their own convention in St. Paul,  Republican representatives are told it is okay to run against the party, YES the BRAND is poison.  So why hasn't this point been made on the presidential level?  Obama hinted at this with "they can win elections but they can not govern."  I am ready to say  about McCain,  Who cares about him?  
Who cares what he did, what he says, what he believes?  He is going to be, if elected, the new (irony) face on the same old failed policies, foreign and domestic.  He needs to be made  irrelevant as a candidate, the GOP's version of the  empty suit.  Each GOP candidate running this cycle is interchangeable with the other regardless of the office, be it Senate, House, or President, i.e. they are Republicans.    
Therefore it doesn't matter that McCain was a POW years ago, what matters is that he he is a Republican NOW.