et’s plunge into the gap between what people say and what other people hear. All kinds of things can grow in that space, many of them poisonous. In that gap, friendships, even marriages, have come apart; wars can start. This week, Barack Obama shone a light into that zone when he talked about the slogan that many Democrats believe cost the party seats in the House of Representatives and Senate last month, a phrase that took flight during the summer of protests against the killing of George Floyd: defund the police. The former president said he too wanted to reform the criminal justice system, ridding it of racial bias, but he feared that using that “snappy slogan” meant “you lost a big audience the minute you say it”. The very change activists wanted moved further out of reach. Far better, said Obama, to say that some of the resources now spent on militarised police should be diverted to other services. If a person, homeless and distressed, is causing disruption in the street, a mental health professional should be dispatched rather than “an armed unit that could end up resulting in a tragedy”. Put it that way, said Obama, and people start listening. As it happens, plenty of campaigners insist that that’s exactly what they meant by “defund the police”. But what too many voters heard was “abolish the police”, by starving them of funds. And those voters didn’t like it, because they reckon that, every now and again, you need a police force. The word “defund” was sufficiently ambiguous – hazy on whether police budgets should be eliminated or merely reduced – that it opened up the gap, that space where distrust, confusion and eventually fear grow. The evidence supports Obama, and not only in the form of the assorted congressional Democrats who say the phrase cost them votes. One Democratic consultant ran a focus group of wavering voters who had considered backing Joe Biden but eventually plumped for Donald Trump. Intriguingly, 80% of these Americans – Trump voters, remember – agreed racism existed in the criminal justice system, and 60% had a favourable view of Black Lives Matter. When the policy was expressed the way Obama put it, 70% of them backed it. But they drew the line at “defund the police”. In other words, the slogan hurt the cause. Obama has been attacked on the Democratic left, criticised for failing to see the urgent necessity of police reform. But that is to miss the point. It’s because change is urgent and necessary that Democrats need to argue for it in a way that wins, rather than loses, support. None of this should be new. The centrality of language to politics is ancient and recurrent. In the 1990s, Republicans had an uphill battle fighting against an “estate tax” on inheritance bequeathed to the wealthy – until they rebranded it “the death tax”. Then they won. But it’s harder for the left which, by its nature, is asking for permission to change the status quo. For that reason, it has to craft language that reassures voters that it understands, and even shares, their starting assumptions – or, at the very least, does not play into their worst fears. The psychologist Drew Westen, whose book The Political Brain has become a classic in this field, counsels that the same voters who might reject “gun control” – fearing an over-mighty state trying to dominate them – often warm to “gun safety” laws. “Medicare for all” might sound wonderful to progressive ears, but what many Americans hear is a proposal to impose a one-size-fits-all system on everyone, even if that means stripping you of a coverage plan you already have and quite like: “Medicare for all who want it” has wider appeal. This has resonance in Britain too. There is nobody on even the mildest wing of the left who is not in favour of equality, and yet even that sacred word might not be quite as appealing as you think. James Morris, onetime pollster to Ed Miliband, has seen how many of the voters that Labour needs to win associate “equality” with levelling down. They think it means everyone getting the same, no matter how hard they work. Those voters don’t like that notion, believing it robs them of the opportunity to get on. And, says Morris, “they also have a moral objection”. They reckon your actions should have consequences, that if you work hard you deserve to be rewarded. For them, “equality” contradicts that. More effective is “fairness”, and the insistence that everyone deserves a fair shot. Keir Starmer might find such advice helpful, but the “defund the police” episode offers another lesson. It is that leaders of political parties don’t get to define their message alone. Biden never uttered the words “defund the police”. Indeed, very few Democratic politicians ever did. And yet, in several key contests that slogan played a crucial role. The Democratic party was held to account for a movement, and a wider cultural left, that went far beyond the precincts it could hope to control. Labour is all too familiar with that danger. In the 1980s, Margaret Thatcher ran against the Campaign for Nuclear Disarmament and the women of Greenham Common, the miners, the universities and often obscure local councillors, as much as she did against Neil Kinnock. Even if he could control his own message, he couldn’t control theirs. In Beyond the Red Wall, another Labour pollster, Deborah Mattinson, reports how distant former Labour voters in Accrington, Stoke and Darlington felt from questions that often exercise the vocal left, whether it be statues, gender or the more outlandish antics of Extinction Rebellion. It’s not that they disagreed necessarily on the issues themselves, rather that they sensed that these were the concerns of people with whom they had nothing in common: “people who didn’t worry about paying for the supermarket shop on a Friday”. And if the left’s loudest voices, amplified by social media, cared so deeply about those other things, surely that meant they didn’t care about people like them. This is the challenge for Starmer and his party. As the row over US police reform illustrates, it doesn’t mean softening the policy, but rather selling it right – and knowing that if you don’t define yourself, somebody else will. Jonathan Freedland is a Guardian columnist Join Sarah Churchwell for a conversation with Joe Biden biographer Evan Osnos in a Guardian Live online event on Thursday 21 January at 7pm GMT, 2pm EST. Book tickets here