"Today it is almost heresy to suggest that scientific knowledge is not the sum of all knowledge. But a little reflection will show that there is beyond question a body of very important but unorganized knowledge which cannot possibly be called scientific in the sense of knowledge of general rules: the knowledge of the particular circumstances of time and place. It is with respect to this that practically every individual has some advantage over all others because he possesses unique information of which beneficial use might be made, but of which use can be made only if the decisions depending on it are left to him or are made with his active coöperation." -- "The Use of Knowledge in Society"
Hayek is here pointing to a distinction made very clear in Aristotle between theoria and phronesis. (Was he aware he was following Aristotle here? I don't know. Does a reader?) Phronesis is practical wisdom, and it applies to particulars, not universals. The mistake of socialist planners was that they thought theoria could replace phronesis in making economic decisions.
And this distinction allows us a very concise and useful definition of "ideology": Political thinking turns into an ideology at the point the thinker comes to believe his/her theories can replace practical wisdom in making political decisions. So, Krugman is wrong: not everyone has an ideology. In fact, we can often point quite accurately to moments in the political life of a nation when ideological politics appears. In Rome it was with the rise of the optimates and populares during the Roman Revolution. In Britain it occurs following the turmoil of the Civil War. And the timing here is no accident: periods of civil chaos leave people longing for clear-cut, easy answers to political problems. But, as we know, there ain't no easy answers.