Political scientists and interest groups often use scaling mechanisms to describe legislators and other political actors. While we know that the (nominal) measures of partisan identification give us some information about ideology (knowing that an individual is a Republican versus a Democrat), we are also used to more ordinal measures of ideology. Thus we have "Blue-Dog Democrats" or "Northeastern Republicans," which convey a sense of ideology in a comparative sense; Blue-dog Democrats are more conservative than a standard Democrat and Northeastern Republicans are more liberal than a standard Republican. But we can also attempt to come up with interval measures of ideology which not only gives the relative position of candidate ideology (e.g., "he is more than conservative than she") but also a sense of the distance between candidates. While we know from Howard Dean's famous talking point that he declared himself part of the "Democratic-Wing of the Democratic Party," we can't really tell from this statement how much more liberal he was than John Kerry. Is a conservative Democrat more conservative than a liberal Republican?
