DW-Nominate - is a scoring system for politicians, running from around -1 to 1, with -1 being very liberal and 1 being very conservative.

G.P.I (Gubernatorial Polling Index) - The GPI is an average of all the polls, weighted against a variable called "weight". This variable represents a combination of the Pollster Rating and the age of the poll. The newer the poll and better the pollster the higher it will be weighted. The age of the poll has more effect on the weight then the pollster rating, with the age making up 75% of the weight and the Pollster Rating making up 25%. However the age weighting will essentially fall off at 50 days and this will get adjusted as we get closer to the race in question.

Pollster Rating - From

PIE [pollster induced error] is expressed as a positive number and reflects the amount of error that a pollster introduces above and beyond that which is unavoidable due to things like sampling variance. The lower a firm's PIE the better.

P.V.I. (Partisan Voting Index) - From The Cook Political Report:

Developed for The Cook Political Report by Polidata, the index is an attempt to find an objective measurement of each congressional district that allows comparisons between states and districts, thereby making it relevant in both mid-term and presidential election years.

While other data such as the results of senatorial, gubernatorial, congressional and other local races can help fine tune the exact partisan tilt of a particular district, those kinds of results don't allow a comparison of districts across state lines. Only Presidential results allow for total comparability.

A Partisan Voting Index score of D+2, for example, means that in the 2004 and 2008 presidential elections, that district performed an average of two points more Democratic than the nation did as a whole, while an R+4 means the district performed four points more Republican than the national average. If a district performed within half a point of the national average in either direction, we assign it a score of EVEN.

hPVI (hybrid Partisan Voting Index) – this is like PVI, but adopted for use at the state level, specifically Minnesota. The only difference between this and PVI is that instead of using the results of the last two Presidential elections I'm using the results of the last Presidential election and the last Gubernatorial election. On the Tables page is a link to the current hPVI tables.

SILVER - A way of combining a legislator's PVI and DW-Nominate score's into a single metric. It is useful for determining how partisan a legislator is in the context of their district or state. On the Charts page is a link to the current SILVER ranking for the state's delegation.