The 11-year-old daughter of a friend of mine recently asked who was the best ever prime minister. Her Labour-supporting mother suggested Attlee, but her grandfather said: “It has to be Wilson, because Attlee went along with the cold war.”

In contrast with the Conservatives and Whigs/Liberals, who have represented privilege for centuries, Labour is just getting started. There have been only six Labour prime ministers and the party has had just 19 leaders. This excludes the two women – Margaret Beckett and Harriet Harman – and George Brown, who have “acted up”, and the multiple occupancies of Arthur Henderson, who led the party three times, and Ramsay MacDonald, who led it twice. Next year will mark the centenary of the Representation of the People Act and the first time that some women and all men got to vote in parliamentary elections. It also marks 100 years of individuals being able to join a party that previously existed as a coalition of socialist, labour and progressive organisations.

How Jeremy Corbyn measures up in the history books depends to a significant extent on how he performs as prime minister. Even the Economist suggests he is likely to make it to No 10. So far, with divisions in the party beginning to heal and serious reconsideration of the Corbyn project by former naysayers, the signs are positive. In advance of a festival to mark the 50th anniversary of Clement Attlee’s death, I’ve been thinking about what makes a great Labour leader.

It seems fair to expect that one criterion is that they win elections, and lead a government as well as a party. Nothing succeeds like success, and without power Labour values can effect progressive change in Britain only marginally. If getting to No 10 were the sole test of greatness, the gold, silver and bronze medals would go to Tony Blair, Harold Wilson and Ramsay MacDonald. Blair gets gold for an unprecedented three consecutive terms as Labour prime minister; Wilson occupied No 10 for two nonconsecutive terms; and MacDonald – Britain’s first Labour prime minister – led two Labour governments. His third term as prime minister of the national government, after his expulsion from the Labour party, doesn’t count.

But there are other criteria to be applied than simply getting and holding on to power at any cost. As Wilson famously reminded the 1962 Labour conference: “This party is a moral crusade or it is nothing.” By this reckoning Keir Hardie (though never prime minister), James Callaghan (still the only leader to serve in all four of the great offices of state) and Attlee stand among the greats. The most fervent pragmatists accept that power on its own is not the point. Judging leadership of any movement or institution must involve some assessment of record, values and personal qualities.

Attlee was the longest-serving leader, with an astounding 20 years, from 1935 to 1955. After taking Labour into Churchill’s wartime coalition and serving with distinction as deputy prime minister, he formed the first Labour majority government after the landslide of 1945. He will always be positively remembered for his role in the postwar political consensus and the founding of the NHS. However, those of us on the left feel more ambivalent when it comes to his role in commissioning Britain’s first nuclear weapon and taking us into the cold and Korean wars.

When it comes to personal leadership qualities, Attlee’s were hardly of the heroic kind. Diffident and pragmatic rather than charismatic in style, he nonetheless inspired his party, and the country, with the 1945 socialist manifesto, and achieved the shock defeat of his flamboyant Conservative opponent, who was famously rude about him: “a sheep in sheep’s clothing” and “a modest man with much to be modest about”. These Churchillian insults may have been wittier than David Cameron’s to Corbyn, but were no less stuffed with class condescension.

Wilson’s wit and intellect are hard to beat, as was his ability to deploy them to hold the broad but always fractious Labour coalition together. From prison reform to humanising abortion laws, abolishing capital punishment and decriminalising homosexuality, Wilson’s leadership institutionalised toleration. And he kept us out of the Vietnam war.

Blair gets credit for peace in Northern Ireland but not for war in Iraq; for Sure Start but not for deregulated financial services or for widening inequality, from which Britain has yet to recover.

Also-rans might also include MacDonald, John Smith and Gordon Brown. MacDonald started well but ended badly; many regard his national government and appeasement as a betrayal of Labour. Brown’s legacy is harder to assess because he was anointed not elected – though will-he-won’t-he indecision over calling an election probably counts against him. Smith is my wild card. He achieved a party hegemony unequalled since Attlee, and would have won the 1997 election on his radical programme.

As Hardie understood, being able to build a coalition within Labour is the key to great leadership

Corbyn’s record will be weighed alongside these men. It’s odd that some commentators who venerate Attlee’s radical manifesto, including significant nationalisation, still dismiss Corbyn’s more modest 2017 version as being of the so-called “hard” rather than “moderate” left. Prior to the last election, we often heard the mantra that Corbyn is “a decent man but no leader”. The decisive shift to the left has been bitterly contested, but since the election an extensive bridge-building programme is under way in the party.

Complementary talents should and will make all the difference to the potential for great leadership, as so clearly demonstrated in the Bevan-Attlee alliance, and Wilson’s great balancing skills. As Hardie understood from its early founding days, being able to build a coalition within Labour is the key to and secret of “great” leadership. The resounding difference between this and last year’s party conference points to Corbyn’s Wilsonian potential to forge a unity coalition. He also has elements of Callaghan’s collective style: respect for cabinet government, a collegiate approach to encouraging openness and trust, and no interest in spin.

Corbyn’s ability to pull the Labour family together may yet surprise, especially if the party’s return to its roots takes the career rebel from leadership to power. But personally, and as someone who sees much to admire in Corbyn’s vision and resilience, the one insoluble problem I have with Corbyn as Labour leader is the fact that he is not a woman. Significantly, he leads a parliamentary party of more women MPs than ever before and more than all the other parties combined, and a 50% female shadow cabinet, with women in key roles.

The crucial importance of a woman leader rests on meeting the socialist-inspired principles of equality, representation and justice on which the party is built, not on any ephemeral gendered qualities. To reflect the makeup of the party and society at large, it’s time for a woman to take her turn. And for those who feel that feminism doesn’t come into it, the call for a woman leader is pragmatic and based on realpolitik: there is currently a powerhouse of serious leadership potential among the women frontrunners.

Succession planning is also a vital test of a leader’s success in the longer term. After at least one term of a Corbyn government, a proud alternative future would be to leave the centre stage of the most populous party in Europe to a woman.

• Rachel Holmes is author of Eleanor Marx: A Life. Her new book Sylvia Pankhurst: Natural Born Rebel is published in 2018