Labour’s poll lead could collapse in the weeks before the general election, the party’s chief campaign strategist has told shadow ministers, as he warned them not to be complacent going into the election year. Morgan McSweeney, Labour’s director of campaigns, recently gave a presentation to the shadow cabinet in which he showed MPs what happened in the months before eight different elections from around the world. In each case, the clear favourite lost after their poll lead disappeared in the weeks leading up to the vote. The presentation, seen by the Guardian, was designed to instil a sense of discipline as the party enters the election year about 18 points ahead in the polls. That message will be repeated by the party leader, Keir Starmer, in a speech on Thursday setting out Labour’s plans for the final months before the general election, which could come as early as May. In his presentation, McSweeney warned: “Polls do not predict the future; nobody has voted in the general election; change won’t happen unless people vote for it.” According to one person who was there, the Labour campaign chief compared being focused on polls to driving while looking in the rear-view mirror. Another attender said: “It showed us what complacency looked like in other countries: a Labour loss.” McSweeney’s message is designed to maintain party unity behind the strategy he has sketched out alongside the party leader, Keir Starmer, and the shadow chancellor, Rachel Reeves. The plan involves proving the party’s credibility to voters by refusing to make election promises unless they are fully funded, while also ruling out major changes to levels of income or wealth taxes. Support for the strategy is likely to be tested in the coming weeks as shadow ministers tussle to ensure their plans are included in the party’s election manifesto, which is due to be completed by the end of this month. Some senior figures in the party believe Starmer should be making bolder policy choices given the party has such a strong lead going into 2024. McSweeney’s presentation was designed in part to rebut this argument. In it, McSweeney, who is one of Starmer’s closest advisers, showed shadow ministers what happened before a range of elections from around the world, including the Australian election of 2019, the Norwegian election of 2017 and the UK election of 2017. In each one, one party went into the election with a significant poll lead, only for it to crumble in the final stages of the campaign. In Australia, Labor were ahead in the polls for well over two years, and had a seven-point lead going at the beginning of the election year. However, the lead collapsed just before the election, giving the governing Liberal-National coalition an unexpected victory. An internal party review later argued Labor had lost because it went into the election promising radical change, allowing the coalition to argue that voting for the opposition party would be a risk. In Norway, the opposition Labour party led by about 20 points two years before the country’s general election but ended up losing after saying it would put up taxes if it won, in an attempt to improve the country’s finances. The party dropped about 5 points during the campaign, which was dominated by discussion about its tax pledge. In the UK in 2017, Theresa May saw a similarly commanding poll lead evaporate after promising to shake up Britain’s social care system in a way opponents said would mean some people having to sell all their assets to pay for their own care.