Cornelius Erfort
I am a Postdoc at the Witten/Herdecke University, working on the project Election Forecasts for the German Federal Election 2025 (zweitstimme.org).
My general interests are in comparative politics and quantitative methods. More specifically, I am working on voter targeting, interest groups, and voting behavior.
In my dissertation, I analyzed how parties use the target and tailor their digital election ads. I was member of the Research Training Group DYNAMICS which is jointly organized by Humboldt-Universität zu Berlin and the Hertie School. During my PhD, I visited the LSE Department of Government for one term (2023). I completed my pre-doctoral studies at the Humboldt-Universität, spent a semester at the CIDE in Mexico City (2017) and have a background in mechanical engineering.
On this website, you can find more information on my research projects and download a copy of my CV (PDF).
Publications
 | Gendered targeting: Do parties tailor their campaign ads to women? The Journal of Politics, forthcoming Are parties communicating differently to women? A growing literature documents gender differences in the political behavior of both voters and politicians, and suggests that this can help or hurt parties electorally. We still know little, however, about whether and how parties adapt their campaign strategies and differentiate their communication accordingly. I analyze how parties strategically vary their communication in ads targeting women using a new comprehensive dataset of over 60,000 Facebook and Instagram ads from 151 parties during the 2019 European Parliament election. Large-scale computational vision identifies the audience-specific tailoring of ads targeted for female audiences in parties' social media ad images and videos. The results show that parties tailor the content of their ads to women. The findings are important because they uncover gendered strategies in parties' campaign communication which have important implications for political representation and opinion formation. @article{erfort_2025,
author = {Erfort, Cornelius},
title = {Gendered targeting: Do parties tailor their campaign ads to women?},
journal = {The Journal of Politics},
year = {forthcoming},
doi = {10.1086/736027},
URL = {https://doi.org/10.1086/736027},
eprint = { https://doi.org/10.1086/736027}
} |
 | Buying Voter Support for Unpopular Policies: Evidence from German Nuclear Power Plants António Valentim, Heike Klüver and Electoral Studies, forthcoming How can governments ensure voters' support for unpopular policies? Policymakers often have to implement policies that are unpopular in local communities, such as the construction of windmills or nuclear power plants. However, little is known about how policymakers can increase local support. We argue that perceived economic benefits increase support for otherwise unpopular policies. We test our argument by studying the consequences of nuclear power plants on support for the Green Party in Germany, a strong opponent of nuclear energy. We collected a novel dataset on the geographic location of nuclear plants and voting records since the 1980s. Using difference-in-differences and instrumental variable designs, we find that the opening of nuclear power plants has a negative effect on the vote share of the Greens. Additional individual-level panel analyses suggest that this effect is driven by economic considerations. Overall, these results are relevant for the study of energy transitions and the design of unpopular policies more generally. @article{erfort_valentim_kluver_2024,
title = {Buying Voter Support for Unpopular Policies: {Evidence} from {German} Nuclear Power Plants},
author = {Erfort, Cornelius and Valentim, António and Klüver, Heike},
journal = {Electoral Studies},
year = {forthcoming},
doi = {10.31219/osf.io/jnarh},
url = {https://osf.io/jnarh}
} |
| | Targeting Voters Online: How Parties' Campaigns Differ Electoral Studies, 2024 How do parties target campaign ads online? Despite the growing importance of digital campaigns, only a few recent studies have analyzed whom parties are targeting. Do parties aim to persuade or mobilize voters? This paper analyzes how parties target and how they differ in their use of targeting using a new and comprehensive dataset, matching data from the Facebook Ad Library with EES survey responses. The dataset contains over 100,000 Facebook and Instagram ads from 148 parties for the 2019 European Parliament elections. The results show that smaller and niche parties have targeting strategies more narrowly focused on their supporters, whereas larger parties target a broader audience. My findings have important implications for research on voter targeting and the ongoing debate about the regulation of campaigns online. @article{erfort_2024,
title = {Targeting voters online: How parties' campaigns differ},
journal = {Electoral Studies},
volume = {92},
pages = {102872},
year = {2024},
issn = {0261-3794},
doi = {https://doi.org/10.1016/j.electstud.2024.102872},
url = {https://www.sciencedirect.com/science/article/pii/S0261379424001306},
author = {Cornelius Erfort},
keywords = {Voter targeting, Party competition, Electoral campaigns, Political behavior}
} |
| | An Election Forecasting Model for Subnational Elections Lukas F. Stoetzer, , Hannah Rajski, Thomas Gschwend, Simon Munzert, and Elias Koch Electoral Studies, 2025 While election forecasts predominantly focus on national contests, many democratic elections take place at the subnational level. Subnational elections pose unique challenges for traditional fundamentals forecasting models due to less available polling data and idiosyncratic subnational politics. In this article, we present and evaluate the performance of Bayesian forecasting models for German state elections from 1990 to 2024. Our forecasts demonstrate high accuracy at lead times of two days, two weeks, and two months, and offer valuable ex-ante predictions for three state elections held in September 2024. These findings underscore the potential for applying election forecasting models effectively to subnational elections. @article{erfort_stoetzer_rajski_gschwend_munzert_koch_2025,
title = {An Election Forecasting Model for Subnational Elections},
author = {Erfort, Cornelius and Stoetzer, Lukas F. and Rajski, Hannah and Gschwend, Thomas and Munzert, Simon and Koch, Elias},
journal = {Electoral Studies},
volume = {95},
pages = {102939},
year = {2025},
issn = {0261-3794},
doi = {https://doi.org/10.1016/j.electstud.2025.102939}
} |
 | The Zweitstimme Forecast for the German Federal Election 2025: Coalition Majorities and Vacant Districts , Lukas F. Stoetzer, Thomas Gschwend, Elias Koch, Simon Munzert, and Hannah Rajski PS: Political Science & Politics, 2025 In this article, we provide a forecast for the German Federal Election of 2025. We use our previous forecasting models to provide national-level forecasts for party vote shares and districtlevel outcomes for candidate votes. We show that the combination of both permits us to calculate both forecasts for coalition majorities in parliament, and "vacant districts" under the recent electoral reforms. @article{Erfort_Stoetzer_Gschwend_Koch_Munzert_Rajski_2025,
title={The Zweitstimme Forecast for the German Federal Election 2025: Coalition Majorities and Vacant Districts}, DOI={10.1017/S1049096525000150},
journal={PS: Political Science & Politics},
author={Erfort, Cornelius and Stoetzer, Lukas F. and Gschwend, Thomas and Koch, Elias and Munzert, Simon and Rajski, Hannah},
year={2025},
pages={1–12}}
} |
 | The PARTYPRESS Database , Lukas F. Stoetzer, and Heike Klüver Research and Politics, 2023 We present the PARTYPRESS Database, which compiles more than 250,000 published press releases from 68 parties in 9 European countries. The database covers the press releases of the most relevant political parties in these countries from 2010 onward. It provides a supervised machine learning classification of press releases into 21 unique issue categories according to a general codebook. The PARTYPRESS Database can be used to study parties' issue agendas comparatively and over time. We extend a recent analysis in Gessler and Hunger (2022) to illustrate the usefulness of the database in studying dynamic party competition, communication, and behavior. @article{erfort_2023,
title = {The PARTYPRESS Database: A new comparative database of parties' press releases},
author = {Erfort, Cornelius and Stoetzer, Lukas F and Klüver, Heike},
journal = {Research \& Politics},
volume = {10},
number = {3},
pages = {20531680231183512},
year = {2023},
doi = {10.1177/20531680231183512},
url = {https://doi.org/10.1177/20531680231183512}
} |
Working Papers
| Parties' issue adaption between elections, R&R , Lukas F. Stoetzer, and Heike Klüver Are parties responsive to short-term changes in election polls? While party responsiveness to election results has received much attention, we know little about the dynamics of issue attention between elections. In this study, we address this question based on the novel comprehensive PARTYPRESS Database. We rely on supervised machine learning methods to build a dynamic measure of parties' issue attention on the basis of more than 250,000 press releases from 68 parties across nine countries from 2010 until 2020. We find little support that losing in the polls leads parties to change their issue attention. When political parties lose support in the polls, they do not clearly prioritize their owned issue, they do not pay more attention to popular issues, and they do not adapt the issue focus of successful competitors. These findings have important implications for our understanding of party responsiveness and the dynamics of electoral competition. @unpublished{erfort_stoetzer_kluver_2024,
title = {Parties' issue adaption between elections},
author = {Erfort, Cornelius and Stoetzer, Lukas F. and Klüver, Heike},
year = {2024},
doi = {10.31219/osf.io/6n3z4},
url = {https://doi.org/10.31219/osf.io/6n3z4}
} | |
| Who Becomes a Lobbyist? Evidence from the US and Germany , Jan Stuckatz, Felix Hartmann, and Heike Klüver Abstract content would go here when available @unpublished{erfort_stuckatz_hartmann_kluver_2024,
title = {Who Becomes a Lobbyist?},
author = {Erfort, Cornelius and Stuckatz, Jan and Hartmann, Felix and Klüver, Heike},
year = {2024}
} | |
| Measuring protest through news articles: A validation approach for manual and semi-supervised methods using government data Protests are an important and well researched aspect of political behavior, making measurement validity crucial. But protests can be difficult to observe. Most studies use newspapers for event coding, introducing a selection bias. Validation usually involves comparing different newspapers or using independent sources. I benchmark a manually and a partly automatically coded dataset from the PolDem project against a large government dataset covering all extreme right demonstrations in Germany from 2005 to 2020. Coverage in newspapers mainly depends on region and size. Machine learning can provide a good estimate about the possible misdetection of events. The results have important implications for the study of protests. Researchers should carefully assess the advantages and shortfalls of media-based datasets. @unpublished{erfort_2024_measuring,
title = {Measuring protest through news articles: {A} validation approach for manual and semi-supervised methods using government data},
author = {Erfort, Cornelius},
year = {2024},
doi = {10.31219/osf.io/g9t8y},
url = {https://osf.io/g9t8y}
} |
Media
 | POLITICO "The city that exposes Germany's deep migration divide" February 18, 2025 |
 | Tagesspiegel "Mit der Erst- und Zweitstimme taktisch wählen: Wie viel Einfluss hat der Brandenburger Wähler?" February 21, 2025 |
 | The Guardian "The far right wants us to play by their rules: Can German Greens survive 'witch-hunt'?" February 12, 2025 |
 | ZEIT ONLINE "Friedrich Merz: Das wären seine Koalitionen" February 4, 2025 |
 | The Economist "Who is ahead in the race for Germany's next parliament?" January 28, 2025 |
 | Abendzeitung München "Wahlrechtsreform und CSU: Wer in München um das Direktmandat kämpft" January 27, 2025 |