Null effects of social media ads on voter registration: three digital field experiments

Civic organisations and progressive campaigns regard digital advertising as an essential method to register to vote low-participation groups, such as ethnic minorities, young voters and frequent home movers like private-sector tenants. Digital strategies appear to be promising in countries like the UK, where the registration process can be completed online, usually in less than 5 minutes, using a web link in the advert. But are typical digital campaigns effective in registering voters? To find out, we provide evidence from three randomised controlled trials: two conducted with advocacy organisations and the third run by the research team, carried out in two types of UK elections (general and local) and assigned either at the aggregate (Study 1 and Study 2) or individual (Study 3) level. Despite wide reach and relatively high rates of engagement, we find that the digital ad campaigns trialed across three studies did not affect under-registered groups’ voter registrations. These null findings raise questions about commonly-used digital advertising strategies to register marginalised groups. They are consistent with other studies that report either null or minimal effects of digital ads on other types of political behaviour.