The quadrennial presidential nominating conventions are the biggest campaign events of the election cycle. Previous studies find that conventions significantly impact national-level candidate preferences; however, scholars have not yet specified the effects that such large campaign events have on residents of the host areas. As fairly uniform and one-sided interventions across years and parties, the conventions offer an opportunity for a cross time, cross-sectional analysis of the local effect of campaign events. We develop a difference-in-difference analysis to show conventions significantly affect the presidential candidates’ county-level vote shares. Individual-level data from panel surveys from before and after the 2000 and 2004 conventions are used to validate the aggregate-level findings. Beyond providing strong evidence of meaningful campaign event effects, the results demonstrate how campaign effects can be conditional on local political characteristics and geography. Overall, we find Democrats are more likely to gain support in convention host communities than Republicans.