The general election is a formality in roughly four out of five American congressional districts. The real decision — who will represent millions of citizens — was made months earlier, often by a sliver of the electorate in a low-turnout primary. This is not a bug in American democracy; it is the operating system.
The phenomenon stems from a confluence of factors that have calcified over decades: aggressive gerrymandering, geographic self-sorting by ideology, and the decline of competitive swing districts. The result is that the median voter theorem, beloved of political science textbooks, applies only to the primary electorate in most races. And that electorate looks nothing like the general public.
The arithmetic of safe seats
After each decennial census, state legislatures redraw congressional boundaries. In most states, the party in power draws lines to maximise its advantage, packing opposition voters into a few districts while spreading its own supporters efficiently across many. The practice is old, but computing power has made it surgical. Modern mapmakers can predict outcomes with startling precision, creating districts where one party's nominee is effectively guaranteed victory.
The consequence is that competition shifts upstream. A Republican in a district that voted seventy-thirty for the party's presidential candidate faces no meaningful threat from a Democrat. The only danger is from the right flank — a primary challenger who can mobilise the most ideologically committed voters. The same dynamic plays out in mirror image for Democrats in urban strongholds.
Who actually votes in primaries
Primary electorates are smaller, older, whiter, and more ideologically extreme than the general electorate. Turnout in congressional primaries often falls below fifteen percent of registered voters. In some cases, a few thousand ballots determine who will represent hundreds of thousands of constituents for years.
This creates powerful incentives for candidates to cater to the activist base rather than the broader district. A moderate position that might appeal to independents becomes a liability if it can be weaponised in a primary. The rational strategy is to secure the nomination first and worry about governing later — if governing requires worrying at all in a safe seat.
The feedback loop
The primary-centric system reinforces itself. Legislators who fear primary challenges vote in ways that please their base, which polarises Congress, which makes compromise harder, which makes the parties more distinct, which makes voters sort themselves more cleanly into partisan camps. Each cycle tightens the ratchet.
Reform efforts exist. California and a handful of other states have adopted nonpartisan blanket primaries, where all candidates appear on a single ballot and the top two finishers advance regardless of party. Alaska uses a similar system combined with ranked-choice voting in the general election. Early evidence suggests these reforms can produce more moderate winners, though the sample size remains small.
Our take
Americans spend enormous energy on presidential campaigns while ignoring the structural reality that most of their representation is decided in obscure spring contests with dismal turnout. The primary system does not merely reflect polarisation; it manufactures it. Until reformers address the nomination process itself, calls for bipartisanship will remain little more than nostalgia dressed as policy.
