How Redistricting Actually Works (and How It Became a Weapon)

Congressional districts are redrawn to a rhythm set by the Constitution: a census every ten years, followed by apportionment (dividing the House’s 435 seats among the states by population) and then redistricting (drawing the actual lines within each state). That is the civics-book version. The 2026 cycle demonstrated how much of it has become optional.

Who draws the lines

In most states, the legislature draws congressional maps and the governor can veto them — meaning whichever party controls state government controls the pen. A minority of states use independent or bipartisan commissions (Arizona, California, Michigan, Colorado among them), created mostly by ballot initiative precisely to take the pen away from self-interested politicians. The result is a structural asymmetry: commission states disarm unilaterally while legislature states draw freely.

The rules that still bind — and the one that doesn’t

• Equal population. Districts must be nearly identical in population — the one requirement courts enforce ruthlessly.
• The Voting Rights Act. Maps may not dilute minority voting strength, which in some circumstances requires drawing districts where minority voters can elect candidates of their choice. The doctrine is in flux, with the Supreme Court narrowing VRA protections in recent terms.
• Racial gerrymandering. Using race as the predominant factor in line-drawing remains unconstitutional — in theory. In practice, proving it, and keeping a ruling intact through the appeals process, has become brutally hard.
• Partisan gerrymandering: no federal limit at all. In Rucho v. Common Cause (2019), the Supreme Court held that partisan gerrymandering claims are political questions federal courts cannot hear. Translation: rigging a map for pure party advantage is, federally speaking, legal without limit. Only state courts and state constitutions can police it.

The gerrymanderer’s toolkit

Two techniques do all the work. Packing crams the opposition’s voters into a few districts they win with 80 percent, wasting their surplus votes. Cracking splinters the remaining opposition voters across many districts they lose with 45 percent. A well-executed pack-and-crack lets a party win a durable majority of seats with a minority of statewide votes — and modern data and mapping software make the execution surgical.

2026: the mid-decade era

The longstanding norm was that maps got drawn once per decade. That norm is dead. In 2025, at the president’s urging, Texas redrew its map mid-decade to add up to five Republican seats; Missouri, North Carolina, and Ohio followed; Democrats counter-drew in California, drawing a Justice Department lawsuit; and the Supreme Court allowed the Texas map to stand for 2026. The full blow-by-blow is in our redistricting-wars scoreboard. The precedent now set: any state, any year, whenever the math demands it. Both parties will live with that ratchet for decades.