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?
Interest groups often come up with "Legislator Scorecards" or rankings. These are typically topical reviews of legislator positions of issues of concern to each group: the National Association of Wheat Growers looks at the positions of Members of Congress on bills related to wheat; Americans for Tax Reform examine votes of Members of Congress on tax issues; and the National Rifle Association determines how much support Members of Congress give to laws related to guns. There are also some broader measures of ideology used by interest groups, such as Americans for Democratic Action which computes ADA scores from a wider measure of votes. Within political science, the most commonly used scores are called DW-NOMINATE scores, which scale political actors based on all roll-call votes. While there are some debates within political science about the propriety of using roll call votes to determine ideology, there is a general consensus that these scores certainly provide some leverage on the issue. They are clearly imperfect, but certainly provide more information than ordinal measures of ideology. DW-NOMINATE scores range from -1 to 1, with one signifying a strong conservative, 0 a moderate, and -1 a strong liberal.
The figure above displays DW-NOMINATE scores for the likely candidates for the Senate race in Florida. I also placed in the chart scores for current Senators Nelson and Martinez, and the median U.S. member from Florida from each party. A few caveats, however, are necessary. There are three plausible candidates below who are not in, and have not been in Congress (Gelber, Rubio, and Hasner). I, however, was able to go back and look at interest group scores from the Associated Builders and Contractor's, Florida Chamber of Commerce, Associated Industries of Florida, the Christian Coalition of Florida, Florida League of Conservation Voters, and National Rifle Association to begin to place these individuals along-side the others. While I did not compute formal bridge measures as political scientists might really want, for the sake of comparison I did examine the scores for both Ron Klein and Connie Mack when they served in the state legislature. I may be able to refine these scores in the future - but these are decent estimates at this point in time. Additionally McCollum has not been in Congress since 2001. I examined McCollum's scores from each of his terms, and there was very little variation. While the votes in Congress can vary from year to year in terms of ideology, thus making year to year comparisons somewhat difficult - for our purposes here to understand these candidates, this does not pose much of threat to that task.
