Less than two months on from one of the worst election defeats in my lifetime, the Labour party finds itself in the middle of a protracted leadership contest, debating its next move over the course of a long, hot summer.

There are those in the party who have argued that Labour simply needs a different leader, but that the politics, plans and policies of the past five years will be enough to get us over the line in 2020 – with a little tweaking, of course.

Others have argued that moving to the left, in response to a Tory government that managed to achieve the difficult feat of gaining an overall majority, is the right response. That the “false consciousness” of modern working people will somehow disappear as the scales fall from their eyes.

Labour will be out of power for a decade if it fails to change, Liz Kendall says Read more

Neither of these approaches will work. Neither recognises the sheer scale of the challenge Labour faces. Both have been tried, and tried, and failed and failed.

Of course, it can be comforting for party members to wrap themselves up in platitudes, to wax lyrical about our values, to regard the electorate as mistaken. Perhaps we should face reality and accept that it was the party rather than the people who got it wrong. In a democracy, to paraphrase Bertolt Brecht, it is the people who choose their government, not the other way around.

As someone who was proud to serve his party and his country as a cabinet minister, I know what this party means to so many people – and what we can achieve. But I also know that we can only achieve anything when we win. Without power, all plans – however well-intentioned – are reduced to mere rhetorical flourishes. Failure to win power is truly the greatest betrayal of those who look to Labour for a prosperous, secure and fairer future.

Do we really have to relearn the lessons of the 1970s and the 1980s? At Labour’s conference in 1983, Neil Kinnock had to tell delegates that “We have to win. We must not permit any purpose to be superior for the Labour movement to that purpose”.

A Labour leader had to tell members of his own party, after a second election defeat, that the only plausible means of making the changes we seek was to win elections. And yet there were two more painful defeats and 14 more years in opposition to a Tory party wreaking havoc before that lesson was finally heeded. We cannot allow ourselves the indulgence of going through a long period in the wilderness again.

It can be comforting to wrap ourselves up in platitudes, wax lyrical about our values, regard the electorate as mistaken

Labour’s only chance of winning in 2020 is to do what we did in 1945, 1964 and 1997 – get back in touch with the electorate, rather than simply telling them they were wrong, and change to meet the challenges of the future.

And that change has never been more crucial than it is today. The challenge Labour faces for 2020 is epic in scale. There are only 24 seats with a Tory majority of less than 3,000. The party must gain 94 seats to win a majority of one. In Scotland, Labour was all but wiped out by the SNP, with seats once considered “safe” now looking difficult to win back in a single term. Seats that were Labour not so long ago now have Tory and SNP majorities of more than 10,000. And all the while Ukip snaps at Labour’s heels.

There are only two candidates in the race who have clearly embraced that need for radical change – but only one who can take Labour in a direction that could win in 2020.

Jeremy Corbyn has plucked at a downcast party’s heartstrings. I don’t doubt his sincerity, but I seriously doubt his judgment. Rehashed Bennism offers Labour only the electoral wasteland it produced before. We don’t have to look in the crystal ball when it’s all in the history books. It would drive an already struggling party even further into that electoral wasteland.

Facebook Twitter Pinterest ‘Jeremy Corbyn has plucked at a downcast party’s heartstrings. I don’t doubt his sincerity, but I doubt his judgment. Rehashed Bennism offers Labour only the electoral wasteland it produced before’. Photograph: Joe Giddens/PA

Liz Kendall, by contrast, is the candidate who has best understood the scale of the challenge, and gives Labour the best possible chance of getting back into government. She has shown that deeply held Labour values need not go hand in hand with an antagonistic approach to those who didn’t vote Labour last time. She has shown she understands that only by working with businesses to create good, well-paying jobs can we build a fairer, more prosperous society. And she knows that Labour won’t be trusted by the British people if they don’t trust us to run the economy.

And make no mistake, Labour wasn’t trusted under Ed Miliband – or by the collective leadership around him. By the election we were polling 20 points behind the Tories on the economy, and the first page of Labour’s manifesto had to include a “budget responsibility lock” in a last-gasp pitch to a sceptical electorate. We can’t allow ourselves to go into the next election with such public doubt over our economic credibility.

Winning voters back from the Tories isn’t an optional add-on; it’s a political and electoral necessity. A recent report from the Fabian society said that 80% of the additional votes Labour will need to win in 2020 must come from those who voted Tory in 2015.

Put simply, we’ll not win those voters back with the Labour choir singing the same tunes we sang as we lost in the last two elections. A lurch to the left would be even more disastrous.

Liz Kendall is the candidate with the optimism, courage and strength to take on the difficult but necessary task of winning the next election. This time the Labour party must not choose to lose again.