When an opposition party hasn’t won a general election for 18 years, you might expect its last success to be cited as a model for how that party could win again. Societies and suitable electoral strategies change over time, of course, but parties that don’t win very often have a limited choice of inspirational examples. Labour is such a party. And in some ways its 2005 victory still looks an impressive achievement. Labour’s third consecutive win – the only time it has managed that – was also the last time any party took a majority of seats in England, Scotland and Wales alike. Unlike all the Tory regimes since, Tony Blair and Gordon Brown’s administrations between 2005 and 2010 could claim to be nationally representative governments. Labour’s overall majority in 2005 was 66, not much smaller than Boris Johnson’s in 2019, which is frequently described as a landslide. Although this year some polls have suggested that the next election could produce a far bigger Labour majority, the party’s long absence from office and the Conservatives’ past electoral recoveries mean that many Labour people and many voters sick of the Tories would probably settle for a 2005-size majority again. Yet that election is not talked about much by Labour politicians and strategists, or by commentators supportive of Keir Starmer’s leadership. Compared with Blair’s other two victories, 2005 is almost forgotten. And if you consider that election result and its context more closely, it is easy to see why. As now, in 2005 the party was on a rightward trajectory, preoccupied by pleasing conservative swing voters and by being at least as “tough” as the Tories in areas such as law and order. As now, Labour had also alienated many Muslim and other Britons by backing a brutal war: in 2005, it was the invasion of Iraq, in which the Blair government had been a key participant two years earlier; now, it is the Israeli destruction of Gaza. During the 2005 election, the improvements Blair had made to public services were overshadowed by Iraq. In a similar way, Starmer’s still relatively radical policies on workplace rights and the environment – already not as visible to voters as they should be – are being further obscured by the acrimony inside and outside the party over his stance on Gaza. Centre-left politics loses much of its moral force when its interest in morality seems to evaporate outside Britain’s borders. All the controversies that had built up around the Blair government helped depress Labour’s vote share in 2005 to 35%, the lowest ever for a party winning a parliamentary majority. Labour’s total vote was even worse: 9.5 million, almost three-quarters of a million fewer than under Jeremy Corbyn in 2019, supposedly the most disastrous result in Labour’s modern history. Even Blair’s generally upbeat memoirs describe his mood on the morning after the 2005 election as “deflated”. Governments rarely get more popular the longer they stay in power, and Labour’s low support in 2005 left it vulnerable to shocks, such as the 2008 financial crisis and subsequent deterioration of the economy and public finances. The combination of a flimsy mandate and hard times for many voters made Labour’s ejection from office at the next election almost inevitable. Given the much more troubled state and society any Starmer government is likely to inherit, for Labour a large vote and majority at the next election are not luxuries – things to feel good and brag about – but political essentials. Whatever he and his shadow ministers say now, a Starmer administration will probably involve intense arguments, both inside the party and between the government and wealthy voters and interest groups, about how to fund public services much better, whether to raise taxes and how to adapt Britain to the climate crisis and a fragmented, unstable world. The party will not emerge from these arguments with all its support intact. The main reason a big Labour majority is possible remains the unpopularity and exhaustion of the Conservative government, the latter clear yet again in this week’s barren and cynical king’s speech. Labour’s improved campaigning in Tory seats, as demonstrated at recent byelections, is also changing the parliamentary arithmetic. Yet a huge Labour vote at the election still feels quite unlikely. Being a party without much media support, or the ancient tribal loyalties enjoyed by the Tories across rural and small-town England, to attract a big vote Labour needs to create a bandwagon, as Blair did in the run-up to his first landslide in 1997, with more and more sections of the electorate enthused at the prospect of Labour government. There are signs Starmer is achieving this kind of momentum in the business world, with lobbyists and executives cosying up to Labour at its annual conference. As the election nears, it’s likely that other interest groups will come out for Labour because they want to back a winner. And yet, apart from wooing the corporate world and what Labour calls “hero voters”, people switching to them from the Conservatives, Labour currently seems more interested in narrowing rather than widening its range of supporters and elected representatives – “shaking off the fleas”, in the memorably contemptuous recent words of a senior party source. The intolerant approach Starmer has followed inside the party is now being applied to the electoral coalition he inherited from Corbyn. Given that many of Labour’s more radical supporters live in safe seats, there is some logic to this strategy. Openly writing off the radicals, the argument goes, won’t seriously weaken the party’s almost impregnable urban strongholds, while making Labour more attractive to voters who dislike the left and live in crucial marginals. Yet politics rarely works that neatly. Supposedly cautious strategies can face unexpected challenges. One has come with the pro-Palestinian protests across the country. As well as their sometimes huge scale, their diversity has been striking. In London last Saturday, the demonstrators were Black, Asian, white, Middle Eastern, queer, straight, young, old, Jewish, Muslim, middle-class, working-class, lads in expensive trainers and families with children: all chanting and waving flags with an energy rare at demonstrations in Britain. As well as outrage at events in Gaza, there was a sense of broader political awakening, and of rebellion against both our main parties. I remember the same feelings on the Iraq marches. Blair ignored them then, and Starmer is trying to ignore them now. If he becomes prime minister, he may wish he hadn’t. Andy Beckett is a Guardian columnist