Having made his promise of an "In/Out" referendum on the UK's EU membership, David Cameron had to follow through. The referendum was to be held on June 23rd 2016 and the campaigning began in April. The question put to voters would decide whether they wanted Brexit, or to remain a member of the EU.
During the campaign, promises were made by trusted politicians on the Leave side, whilst Remain focussed its attention on the benefits EU membership brought, and the disastrous consequences of a "No Deal" Brexit. However, these were dismissed as "scaremongering".
Before the vote, many assumed that Remain would easily win. Of the nineteen political parties which expressed an opinion, only four supported Leave. Opinion polls also suggested that Remain would win but, as the day grew closer, the gap between support for the two sides shrank. The referendum result would be too close to predict.