The role of social media ads for election outcomes: Evidence from the 2021 German election.

Social media ads have become a key communication channel in politics. However, the relationship between political ads from social media and election outcomes is not fully understood. Here, we aim to estimate the association between online political advertising and election outcomes during the 2021 German federal election. For this, we analyze a large-scale dataset of 21,641 political ads from Facebook and Instagram that received ≈126 million impressions. Using regression analysis, we show that political advertising on social media has a positive relationship with a candidate's election outcome and may even sway elections. All else equal, ≈200,000 additional impressions are predicted to increase a candidate's votes by 2.1%. We further use a causal sensitivity analysis to evaluate how unobserved confounding may affect our estimates. We find that the estimated impact of ads cannot be reasonably explained away, highlighting the significance of social media for election outcomes.