California and Texas have been sparring over redistricting. Republicans in Texas want to redraw their electoral map to win another five congressional seats, and California has threatened to respond with more Democratic seats to match. Each side accuses the other of bad behavior. Governor Abbott of Texas has called the current California redistricting plan a gerrymander, and Governor Newsom of California has said Texas’s plans undermine core tenets of American democracy. The reality is more complicated than either presents, and gets wrapped up in chance, competition, and the peculiarities of congressional districting.

A partisan gerrymander redraws electoral maps so that they favor the political party in control of creating those maps. It aims to win that party more seats without needing to win more votes. The gap between a party’s seat share and vote share is therefore a reasonable way to gauge the partisan advantage it enjoys under a given plan. The larger the gap, the greater the advantage.

But the path from advantage to gerrymander can be complicated. A particular partisan advantage might emerge by accident, either because the author of the plan was maximizing some other goals and didn’t know the partisan consequences, or because the political dynamics of future elections turned out differently than expected.

Moreover, single-member district elections—like the ones for the US House of Representatives—have historically had a natural “winner’s bonus” that usually gives the majority party a higher seat share than vote share, even without a gerrymander. For example, a party winning 55% of the votes would rarely win exactly 55% of the seats. It would almost always win at least a few percentage points more, and sometimes far more than that.

So a modest seats-votes discrepancy is normal and not a sign of gerrymandering. In fact, a common measure of fairness, the “efficiency gap,” assumes that a party’s seat share should increase two percent for every one percent increase in vote share: a baked-in winner’s bonus.

California’s existing plan was drawn by an independent redistricting commission, and Texas’s by its state legislature. Yet coming out of the 2024 election, California’s had by far the larger seats-votes gap. Republicans in Texas won 66% of the US House seats off 56% of the major-party vote (a pro-Republican efficiency gap of 4%), while Democrats in California won 83% seats off 61% of the vote (a pro-Democratic efficiency gap of 11%). When Governor Abbott says California is gerrymandered, he likely has this contrast in mind.

But the real contrast between the California and Texas plans is not partisan gerrymandering so much as partisan competition. Texas Republicans in 2021 drew themselves such an uncompetitive plan that it left them little opportunity to pick up more seats when they started winning more votes. The plan would have been a boon for them in 2020—when Biden performed well in Texas—because it might have protected them from losing seats. But the plan wasn’t used in 2020, and Republican vote shares have only climbed since then, leaving the party with nothing to show for their gains in popular support.

California’s plan is far more competitive. One in five California seats was claimed by less than 10% in 2022, and one in six was close (by this same metric) in 2024. Just one in 20 seats—2 seats out of 38—fit the bill in Texas in either election. (Other thresholds for competitive districts produce the same basic pattern.)

Furthermore, Democrats won their three new seats in 2024 by extremely narrow margins. A switch of just 8,833 votes out of 15 million cast statewide would have been enough to reverse the outcomes in all three. Without a Democratic win in those three seats, California’s efficiency gap (5%) would look about like the one in Texas.

Both state parties are talking about padding their seat totals, so this status quo might change. Five more Republican seats in Texas would balloon their efficiency gap advantage from 5% to 17%. California Democrats, meanwhile, want to add five seats to their current total, turning a lucky advantage into overwhelming dominance (an efficiency gap of 20%).

For both parties, good representation of their own electorates is beside the point. Instead, their goal is to stay balanced at the national level. At the moment, the national efficiency gap for the House has a slight Democratic advantage of about seven seats: Republicans have a majority of votes and seats, but their seat share is not as high as the modest winner’s bonus of the efficiency gap would expect.

That means Texas, acting by itself, would arguably bring the overall chamber closer to neutral, even while making representation for its own residents more biased. California’s response, on the other hand, would increase bias for both. Neither national effect would be very large, but either could make the difference in a very close election.

The real story is less the fight between California and Texas than the broader war their fight might provoke. If more states enter the fray and gerrymander their own plans, the outcome will probably favor Republicans but will be difficult to predict. The possibility of more biased representation—both nationally and separately for each state—is real.

The absence of a common national process or standard looms large over this possible battle royale. National guardrails could bind each state and avoid these spiraling dynamics. Congress and the president have the authority to regulate congressional elections if they choose, and the potential chaos of this moment may prove painful enough that both parties lay down their arms. Whether that happens, and when, remains to be seen.