New actors, from civil society organisations or individuals, can play a key role in the campaign, not only spreading the candidate’s messages online but also buying ads to reinforce or weaken the candidates’ positions. These actors can act without a link with the official campaign and even work outside the national barriers. Against this background, the responsibility of social media platforms within the framework of current political / campaign finance regimes to ensure transparency and accountability of ad placement, expenditure and attribution in order to better inform citizens of the context in which electoral choices are being made, gains critical importance.