5) The ACU primarily looks at votes, and it averages them over a career. There are other important factors in judging a candidate which the ACU does not adequately take into account.
For example, on how many occasions has McCain expressed as much enmity toward liberals as he routinely does toward conservatives. For that matter, when has he put forth any particular opposition to liberals beyond punching a 'yes' or 'no' vote?
If someone votes the right way sometimes, but does nothing else to demonstrate conservatism, what reason is there to believe the person will be conservative in a position that requires real action?
You missed the whole point, i.e. don’t tell me there is zero difference between The Evil Witch and McCain.