What do Ronald Reagan and Spain’s radical Podemos party have in common? Little, you might imagine. The former was an unapologetic champion of letting the market run riot; the latter is, in part, a rebellion against that dogma. But both defined their contrasting philosophies in a similar way: with hope, optimism and empowerment. Reagan won two landslide elections; while less than two years after it was founded, Podemos – though still not in government – became one of Spain’s three major parties.

A cursory glance at opinion polls would suggest that, for any progressively minded person, talk of hope and optimism currently means delusion and denial. Labour has six weeks to chip away at a colossal Tory poll lead. The defeatist approach is to think it’s too late and people have already made up their minds.

Labour needs a clear message to hammer away at. The MP Paul Flynn jokes that Lynton Crosby – David Cameron’s “Lizard of Oz”, now hired by Theresa May – has implanted a chip into the brains of Tory MPs, compelling them to say “strong and stable” every 18 seconds and “coalition of chaos” ever 38 seconds. Funny, but the Tory approach is painfully effective. And Labour’s own approach must be infused with optimism – learning from the effective political campaigns of the past.

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Take Reagan. In the 1970s the US was afflicted by a sense of unease and decline. “Morning again in America!” was Reagan’s mantra. Of course, his actual legacy was a new economic settlement marked by de-industrialisation and stagnating wages. The bitterness and resentment that legacy spawned is one reason why a bigoted former reality TV star is now the world’s most powerful person. But at the time Reagan’s optimism was infectious.

He quoted the US poet Carl Sandberg: “I see America not in the setting sun of a black night of despair; I see America in the crimson light of a rising sun fresh from the burning, creative hand of God. I see great days ahead for men and women of will and vision.” America’s best days were ahead, he declared. And as well as optimism, he offered empowerment. “The time is now, my fellow Americans, to recapture our destiny, to take it into your own hands.” It made Americans feel good about themselves. It made them feel as though they had power, and that the future would be brighter – because of them.

Podemos is at the other end of the spectrum, but look at how it frames its message. A Spanish political party that wants to talk about misery has no shortage of material. The economic crisis left half of younger Spaniards out of work, and hundreds of thousands of Spanish families were evicted from their homes. Yet Podemos has focused relentlessly on optimism. “When was the last time you voted with hope?” the party asked in the 2014 European elections, its breakthrough moment. “We think we represent not only the vote of the ‘outraged’, but also a vote of hope,” declared the party’s pony-tailed leader, Pablo Iglesias.

Britain’s official leave campaign waged a campaign of fear, but its slogan – “Take back control"– cut through

Barack Obama is famed, of course, for running his 2008 presidential campaign – after the George W Bush years of war and financial collapse – on hope and empowerment. “Yes we can!” was a rallying cry – also adopted by Podemos (¡Si se puede!) – to inspire a sense that problems could be overcome with collective resolve and determination.

Obama would later paint a story of the US that emphasised its best qualities. “That’s the America I know,” he declared. “That’s the country we love. Clear-eyed. Big-hearted. Undaunted by challenge. Optimistic that unarmed truth and unconditional love will have the final word.” Did Donald Trump go on to run a campaign of hope? Manifestly not. But “Make America great again” certainly was about empowerment. Americans had a choice to infuse their country with greatness once more: that’s how many sincerely felt.

Or indeed watch Bernie Sanders’ “America” political ad: he didn’t win the Democratic nomination, but he came a lot closer than many predicted. Set to the tune of the Simon and Garfunkel song of the same name, it showcases everyday Americans in small towns and big cities, on farms and in family homes. As the song reaches its climax – and Sanders walks on to a stage surrounded by cheering crowds – the lyrics blast on the screen: “They’ve all come to look for America.” By the end of it, I practically wanted to stand, salute and belt out The Star Spangled Banner.

Britain’s official leave campaign may have waged a campaign of fear, but its slogan – the one that really cut through – was “Take back control”. How much more empowering can a slogan be? “I just think we needed to take back control,” was the kind of thing I’ve heard spontaneously uttered by leave voters over and over again. Some felt they no longer had a say over their future. A simple slogan tapped into this feeling, and how powerful it was.

Facebook Twitter Pinterest ‘We think we represent not only the vote of the outraged, but also a vote of hope,” declared the pony-tailed party’s leader, Pablo Iglesias Photograph: Pierre-Philippe Marcou/AFP/Getty Images

There are many other examples. Labour’s “Let us face the future” campaign of 1945 was dripping with hope: “Victory in war must be followed by a prosperous peace,” it demanded. “The nation wants food, work and homes. It wants more than that – it wants good food in plenty, useful work for all, and comfortable, labour-saving homes that take full advantage of the resources of modern science and productive industries.”

It’s a statement of the obvious that Labour enters this election in a weak position. There is always the temptation on the left – and I include myself here – to focus on injustice and the misery it brings. Food banks, zero-hours contracts, poverty, a lack of decent homes, and so on. Only a few feel such hardship: life for those in the middle is often marked by insecurity and struggle, but not squalor. In any case, it doesn’t rouse people. It is depressing, and grim – and makes people feel bad about themselves and their country. It’s not empowering.

Instead, the campaign should harness a sense of optimism, hope and empowerment. Together, we can build a different sort of Britain. This is a country with great potential. There is so much we can be proud of and build on. There is no problem we cannot solve. We’ve had great challenges in the past, and we’ve always won them. Our history is littered with stories of courage, determination and resilience in the face of adversary.

Let’s capture that all over again. Dare to have dreams. A society run in the interests of people’s needs and aspirations – not profit for a few – is possible. A wealthy nation can cure all of its ills: we just need the willpower and determination. That’s the prism through which every slogan, every vision, every policy offer should be seen.

Maybe the defeatists are right, and it’s too late to turn it around. But if it isn’t, it will be optimism, hope and empowerment that will make the difference.