Remain campaign operatives floated a plan to convince Corbyn to make a public gesture of cross-party unity by appearing in public with the prime minister. Polling showed this would be the number one play to reach Labour voters.
Senior staff from the campaign begged Corbyn to do a rally with the prime minister, according to a senior source who was close to the Remain campaign. Corbyn wanted nothing to do with the Tory leader, no matter what was at stake. Gordon Brown, the Labour prime minister whom Cameron vanquished in 2010, was sent to plead with Corbyn to change his mind. Corbyn wouldnt. Senior figures in the Remain camp, who included Camerons trusted communications chief Craig Oliver and Jim Messina, President Obamas campaign guru, were furious.
Even at more basic levels of campaigning, Labour were refusing to cooperate. The party would not share its voter registration lists with Stronger In, fearing the Tories would steal the information for the next general election. Our data is our data, one senior Labour source said when asked about the allegation.