The House's Republican bias is gone. But the gerrymander lives.

Washington Post

03-03-2025

For the first time in two decades, the efficiency gap is close to zero.
(Michelle Kondrich/The Washington Post)
Nicholas O. Stephanopoulos is the Kirkland & Ellis professor of law at Harvard Law School. Christopher Warshaw is a professor of political science at George Washington University. Eric McGhee is a co-founder and board member of PlanScore.org.
Here's another assumption punctured by the 2024 election: that gerrymandering and Democratic vote-clustering give Republicans a structural advantage in the battle for control of the House of Representatives.
For more than two decades, the House was consistently biased in Republicans' favor. Votes cast for GOP candidates translated into congressional seats more efficiently than did votes for Democrats. In 2012, most dramatically, Republicans won a majority of more than 30 seats with a minority of the aggregate nationwide vote. Political observers debated whether this skew was 'natural' — a by-product of the country's political geography — or the result of Republican gerrymandering. But few doubted that the House was, in fact, tilted to the right.
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Now, that fixture of American politics is gone. In the 2022 and 2024 elections, according to standard measures of partisan bias, the House exhibited no pro-Republican lean at all. Of course, Republicans won narrow majorities in 2022 and 2024. But they did so because they won narrow pluralities of the total House vote. For the first time in a generation, both Republicans' control of the chamber and their slim governing margins accurately reflected voters' preferences.
How do we know the House's pro-Republican skew has disappeared? One common measure of bias, the efficiency gap, compares the parties' respective shares of 'wasted' votes: those cast either for losing candidates or for winning candidates in excess of the threshold for victory. By this metric, the House tilted sharply in Democrats' favor from the 1970s through the early 1990s. Then in the 2000s and 2010s — a period marked by aggressive Republican gerrymandering — it leaned right. Over the past two elections, the House's efficiency gap was close to zero but marginally pro-Democratic.
Thanks to this shift, legislative divisions over the next two years will mirror cleavages in the electorate, at least in partisan terms. And when it's time to vote again, whichever party earns a plurality of the total votes cast in House races is likely to win the speaker's gavel. Neither party should expect its share of House seats to be too inflated or deflated relative to its popular appeal.
What spurred this change? Part of the story is a decline in extreme Republican gerrymandering. In 2012, six states' congressional plans had pro-Republican efficiency gaps of two or more seats. This decade, only one state's map (North Carolina's for the 2024 election) was as tilted toward Republicans. In several states, newly minted commissions or successful lawsuits prevented Republican lawmakers from crafting maximally advantageous maps.
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At the same time, the 2020s feature more highly pro-Democratic plans. In 2012, no map had a pro-Democratic efficiency gap of at least two seats. This decade, Illinois's Democratic gerrymandering boosted Democrats by 3.5 seats on average. California's commission-drawn map netted them roughly 4.5 bonus seats, possibly because the spatial patterns of the state's voters favor Democrats. The Democratic map selected by New Jersey's commission also averaged a pro-Democratic skew of two seats. And New York's revised 2024 plan leaned toward Democrats by slightly more than two seats.
California's and New Jersey's records may suggest that commissions tend to enact pro-Democratic maps. But other commissions, such as Arizona's and Colorado's, approved pro-Republican plans. Michigan's new commission adopted an almost perfectly fair map. In all, the nine states with redistricting commissions had plans averaging a near-zero efficiency gap (in percentage point terms) in 2022 and 2024. So commissions remain an obvious institutional fix for partisan gerrymandering. They may not guarantee fair maps, but they do raise their likelihood.
The House's reduced tilt also reflects the country's changing political geography. For years, some have argued that Republicans 'naturally' benefit from redistricting because Democrats squander too many votes in safe urban districts. In 2024, however, cities swung to the right as Republicans made large gains among young and minority voters. That meant Democrats won most urban districts by considerably tighter margins. Concurrently, rural and exurban areas backed Republicans to an even greater extent. Districts there are now about as blood-red — i.e., as inefficient — as their deep-blue counterparts in cities.
The evaporation of the House's bias is a milestone, but it may be short-lived. Some states could redraw their districts in the middle of the decade (a move New Hampshire and Ohio are considering). All states will redistrict after the 2030 Census, resulting in plans that could durably advantage either party. Geographic voting patterns might revert to earlier configurations that favored Republicans. And incumbent-protecting maps in Texas and elsewhere might prevent Democrats in particular from flipping many seats even if they win many more votes.
With these scenarios on the horizon, today's unbiased House shouldn't be a pretext for putting off redistricting reform. The House isn't balanced because most states have fair congressional plans; to the contrary, many states have unfair plans, but Democratic and Republican gerrymanders happen to offset one another almost perfectly. This equipoise is fortuitous, but it continues to leave many Americans poorly represented by their states' congressional delegations. Redistricting abuses also remain rampant at the state and local levels. These legislatures' biases can't be balanced by maps elsewhere being tilted in the opposite direction.
The need to curb gerrymandering, then, is as urgent now as when it previously distorted the House as a whole.