U.S. presidential campaigns spend hundreds of millions of dollars each election cycle to maximize their chance of electoral victory. Media coverage analyzes individual campaign advertisements, activities, and decisions as if they are hugely influential. Yet, whether an election is close or not is due to factors that are outside the control of electoral campaigns, such as wars and pandemics or even candidate characteristics. In fact, roughly two-thirds of the variance in U.S. presidential election outcomes—where both sides always run substantial campaigns and frame these fundamentals for voters—can be explained by simple models using just economic performance and whether the incumbent is running. Several strands of academic literature may support a perception that some small campaign decisions can make big differences in voter attitudes and behaviors [e.g., how arguments are framed or where field offices are placed in battleground states]. This work likely overstates the effect of campaigns in the field, though, because it isolates specific elements from the chaotic din of real-world politics and therefore either cannot control for the endogenous strategic decisions campaigns make or does not occur in environments when voters' partisan identities are fully activated. By pulling together disparate strands of research and situating presidential campaigns in their broader electoral, social, and media contexts, we argue that sizable persuasive effects from campaign activities seem very unlikely to be observed in real-world elections.
Nickerson, David W., and Todd Rogers. "Campaigns Influence Election Outcomes Less than You Think." Science 369.6508 (September 2020): 1181-1182.