The NTU (which consists of about 10 people, BTW), does have some kind of mystical power to decide who is or isn't conservative. They themselves aren't conservatives - their founder is a libertarian, not a conservative.
The NTU gives points to representatives for voting against defense spending, for example.
His NTU rating is one data point which has to be weighed against others - like his defeatism, his treasonous attitude and his liberal voting record.