In contrast to non-partisan Get Out the Vote (GOTV) campaigns, political parties do not aim to increase turnout across the board. Instead, their principal goal is to affect the outcome of an election in their favor. To find out how they realize this aim, we carried out a randomized field experiment to evaluate the effect of campaign visits and leafleting by Conservative Party canvassers on turnout in a marginal English Parliamentary constituency during the 2014 European and Local Elections. Commonly-used campaign interventions, leaflets and door-knocks, changed the composition of the electorate in favor of the Conservative Party, but did not increase turnout overall. Supporters of rival parties, particularly Labour self-identifiers, were significantly less likely to mobilize in response to Conservative campaign contact than Conservative supporters. In contrast to the non-partisan GOTV literature, we show that impersonal campaign leaflets were as effective in shaping the local electorate in the Conservative’s favor as personal visits. The common practice of contacting all constituents irrespective of their party preferences was effective as a campaign tactic, but had no civic benefits in the aggregate.