Your statement is either true or false and it doesn’t take much to prove that it is false.
The only votes that are FOR obama are those actually cast for obama.
A non voter or third party voter does not add to Obama’s vote count, nor does it subtract from McCain’s count.
So there is no ‘effective’ addition or subtraction of either candidate at all.
Your premise is false. Just accept it and move on.
It would only be false if they were tied.
This is beyond you. I will move on now.