We make projections by adjusting the partisanship of a district based on prior election results. The adjustment depends on the number of terms an incumbent has served and whether the incumbent's worst performance from the last two elections was better or worse than the partisanship of the district.
The following variables control how each adjustment is made. The default value is in parentheses.
% decrease for "overrachieving" incumbent (60%)
The percentage decrease from an incumbents worst performance down to the partisanship of the district. Applies to 3 or more term incumbents whose worst performance is better than the partisanship of the district.
Absolute reduction for "underachieving" incumbent (1%)
The projection equals the incumbents worst performance minus the absolute reduction. Applies to 2 or more term incumbents whose worst performance is worse then the partisanship.
% adjustment to better 2nd election (33%)
If a two-term incumbents second performance is stronger than the first, we adjust the worst performance 33% of the way from the weaker (first) performance to the stronger one.
% decrease if previous race uncontested (35%)
If the second race was uncontested, we put less weight on the 2nd performance.
% decrease for "overachieving" new incumbent (67%)
If a new incumbent performs better than partisanship, we reduce the projection 67% of the way from the worst performance down to the partisanship.
% increase for "underachieving" first-termer (33%)
If a freshman performed worse than partisanship if her first election, we increase her projection 33% of the way up to the partisanship.
Buffer of absolute increase/decrease of 5.5% for open seats (11%)
In open seats, the projection equals the partisanship of the district minus 11%, with no projection below 50%. So a 65% partisan district is projected to be a 54% Democratic win.