Data

Inside Elections’ Baseline captures a state, county, or congressional district’s political performance by combining all federal and state election results over the past four election cycles into a single score. This index aims to approximate what the “typical” Democrat or Republican might receive in any given area.

To calculate Inside Elections’ Baseline, we include all contested partisan elections for federal and statewide offices (executive or constitutional) in the four most recent cycles, as well as any special or off-year elections during that span. The only district-based elections we consider are U.S. House races and their specials.

These results are then combined into a trimmed mean, or an average of all previous elections omitting the highest and lowest values for each party, to estimate the strength of a “typical” Democratic or Republican candidate. This project requires a comprehensive collection of statewide election results by congressional district. But because most states don’t officially report down-ballot races at this level, we calculate them manually.

1. Data
   Our first step is to collect data for each election of interest. We obtain precinct-level results from a few main sources: official returns were pulled directly from state or county elections websites whenever feasible, while gaps were filled with invaluable data from VEST, MIT Election Lab, Redistricting Data Hub, OpenElections, and other repositories.
2. Assigning Precincts to Districts
   A key part of this process is determining which precincts fit into each district. For elections conducted alongside a set of districts, this is fairly straightforward. We simply check the corresponding House results to see where each precinct was assigned, then apply that to the other races, with split precincts handled using the “votes cast” method.
   In cases when no corresponding House contests align with the boundaries — such as any election before 2022 evaluated under the 2022 lines, or any earlier elections in a state that undergoes mid-cycle redistricting — we use another standard approach: take a shapefile of precinct results, disaggregate them to Census blocks, then recombine the results up to the district level.
3. Putting It Together
   Once all precincts have been properly allocated and split, the final step is to add everything up to the district level; this process is repeated for each election of interest in each district. To calculate each party’s Baseline, simply take the trimmed mean — an average omitting the highest and lowest values — of all previous elections over the past four cycles.

Vote Above Replacement (VAR) measures the strength of a political candidate relative to a typical candidate from their party within the same district or state. That initial benchmark is derived using Inside Elections’ Baseline: VAR is simply the difference between a candidate’s share of the vote and their party’s Baseline. A higher VAR indicates a strong performance relative to expectations.