Which states contributed most to partisan gerrymandering wins after the 2010 redistricting?
Executive summary
Republican-controlled redistricting after the 2010 census produced some of the clearest partisan gains: research and reporting tie the 2010 REDMAP strategy and Republican trifectas in many states to maps that advantaged Republicans in congressional and state-legislative seats [1] [2]. Analyses find that partisan mapmaking after 2010 produced substantial state-level advantages (e.g., Pennsylvania, Wisconsin, Ohio, North Carolina) even as national-level cancellation left only a modest net Republican gain in some studies [3] [2] [4].
1. The post‑2010 landscape: Republicans seized mapmaking power
The 2010 redistricting cycle followed a sweep of state legislative gains by Republicans and an organized strategy—REDMAP—that targeted state legislatures to control map lines; this allowed Republicans in many states to draw congressional and legislative districts designed to preserve and expand their majorities [1] [5]. Multiple sources document that Republicans held trifectas in key states (governor plus both legislative chambers) and used modern mapping tools to craft precise maps [2] [6].
2. States most frequently cited for partisan wins after 2010
Reporting and academic summaries repeatedly single out Pennsylvania, Wisconsin, North Carolina and Ohio as states where 2010-era maps produced notable partisan outcomes: Pennsylvania’s 2011 map produced a 2012 result where Democrats won more votes but Republicans won most seats [3]; Wisconsin’s post‑2010 maps were drawn when Republicans controlled the legislature and governorship and show evidence of cracking around Milwaukee [2]; Ohio and North Carolina are similarly highlighted in redistricting discussions of the 2010 cycle [5] [7].
3. What “wins” look like on the ground
State examples show different mechanisms: Pennsylvania’s congressional map produced a seat distribution favoring Republicans despite a Democratic popular vote advantage in 2012 [3]; Wisconsin’s state‑assembly maps illustrate packing and cracking patterns engineered by the party in power [2]. These are the concrete outcomes observers point to when naming “most affected” states from the 2010 round [3] [2].
4. National studies: broad practice, modest aggregate advantage
Algorithmic and statistical work finds partisan gerrymandering was widespread in the 2010s but that across all states some biases cancel out — though researchers estimate a small net pro‑Republican effect (about two extra House seats on average in later cycles) after accounting for geography and legal constraints [4]. That nuance means state‑level wins can be large even if the national total narrows [4].
5. Competing interpretations and reform responses
Advocates and some scholars emphasize organized Republican success in 2010 (REDMAP) and its durable effects in targeted states [1]. Others and some empirical studies stress that geography, legal rules and later court fixes or reforms (e.g., commissions or state court rulings) complicate simple “Republicans won everywhere” stories; reforms and litigation in places like Pennsylvania and Ohio forced map changes or new rules [8] [9]. Both strands appear across the sources [1] [8] [4].
6. Limits of the available reporting and what’s not in these sources
Available sources document state examples and broad analyses but do not provide a single ranked list of “which states contributed most” in numerical terms; sources show prominent examples (Pennsylvania, Wisconsin, North Carolina, Ohio) and national-level estimates of net advantage [3] [2] [5] [4]. Detailed state-by-state seat‑gain tallies attributable solely to partisan mapmaking after 2010 are not compiled in the provided materials — that specific ranking is not found in current reporting (not found in current reporting).
7. What to watch next and the implicit agendas in the sources
Academic pieces focus on measurement and baseline simulations and therefore emphasize methodological limits and small aggregate effects [4]. Advocacy and journalistic accounts (e.g., PRO‑Republican strategy pieces, Brennan Center explanations) highlight intentional political strategy and push for reforms; these sources have an implicit reform agenda or partisan-concern framing [1] [10]. Readers should weigh technical studies that quantify net effects against advocacy reporting that emphasizes state‑level examples and political organization.
8. Bottom line for your question
If you ask which states “contributed most” to partisan‑gerrymandering wins after 2010, the sources repeatedly point to Pennsylvania, Wisconsin, North Carolina and Ohio as prime examples of post‑2010 maps producing clear partisan advantages, with REDMAP and Republican trifectas central to that outcome [3] [2] [1] [5]. At the same time, national analyses show cancellation across states that reduces but does not erase a modest Republican advantage [4].