Why redistricting is so important, in 3 charts

Texas Republicans' move to redraw their congressional map mid-decade and Democrats' retaliatory redistricting efforts have captured national attention for a very simple reason: How House districts are drawn can shape American politics for years

Texas Republicans' move to redraw their congressional map mid-decade and Democrats' retaliatory redistricting efforts have captured national attention for a very simple reason: How House districts are drawn can shape American politics for years.

Gerrymandering generally reduces the number of competitive races, and it can lock in nearly immovable advantages for one party or another. Under the new map proposed in Texas, no seat’s presidential vote would have been decided by single digits in 2024, and Republicans would have a path to pad their narrow congressional majority in the 2026 midterm elections. This means more people could reside in congressional districts under solid control of one party.

NBC News analyzed how the question of who draws the maps — and how they do it — can shape elections for years afterward.

Who draws district lines can make the difference between contested general elections in a state in November and elections that are barely more than formalities.

NBC News analyzed every House race in the country from 2012 to 2020, the last full 10-year redistricting cycle, based on how each district was drawn. In states where state legislators drew the maps, single-digit races (elections in which the winners won by less than 10 percentage points) were rarest. Only 10.7% of House races fell into that competitive category.