What Does a Satellite Campaign Do? Momentum, the Labour Party and Jeremy Corbyn on Facebook in the 2017 General Election

Satellite campaigns, organisations that campaign for a party without being part of it, became a visible part of British elections in 2017. The best known was Momentum, formed to support Jeremy Corbyn's leadership of the Labour Party. I ask what Momentum's Facebook page did that Labour's own pages did not. I compare all 153 retrievable posts from Momentum's page in the month before the 2017 general election with 278 posts from the Labour Party page and 144 from Corbyn's page, each hand coded for 154 features. The party page ran a campaign for votes: 85% of its posts asked for a vote, 66% made a pledge and 80% used the party slogan. Momentum asked for a vote in 12% of posts. Instead about half its posts asked people to help on the doorstep, volunteer or sign up to campaign, against 3% to 7% on Labour's pages, and it used humour in a quarter of its posts. Corbyn's page was close to the party page overall, but on all eleven reliably coded features where it differed significantly from the party page, it differed in Momentum's direction: less policy, fewer calls to vote, more news clips and more attacks on the opposition leader. On the Labour side of the 2017 campaign, the leader's page sat between a formal party campaign and a satellite that asked its followers to campaign.Version 2 (2026) replaces the 2021 working paper. It reanalyses all codes with formal tests, corrects for multiple comparisons and reports which codes were reliably measured. Also available at https://doi.org/10.5281/zenodo.23296711