Social media are now a routine part of political campaigns all over the
world. However, studies of the impact of campaigning on social platform have
thus far been limited to cross-sectional datasets from one election period
which are vulnerable to unobserved variable bias. Hence empirical evidence on
the effectiveness of political social media activity is thin. We address this
deficit by analysing a novel panel dataset of political Twitter activity in the
2015 and 2017 elections in the United Kingdom. We find that Twitter based
campaigning does seem to help win votes, a finding which is consistent across a
variety of different model specifications including a first difference
regression. The impact of Twitter use is small in absolute terms, though
comparable with that of campaign spending. Our data also support the idea that
effects are mediated through other communication channels, hence challenging
the relevance of engaging in an interactive fashion