Alan Johnson, a former union official, former home secretary and one of the most highly regarded figures of the New Labour high guard has endorsed Yvette Cooper (pictured above) for the Labour leadership contest.

It’s been a surprising election, and the most beguiling twist of all has been the emergence of Jeremy Corbyn, the 66-year-old socialist, as the frontrunner among Labour rank-and-file. Polls consistently show that Corbyn has a wide lead over Cooper, shadow health secretary Andy Burnham and Liz Kendall for first preference votes. Corbyn has won the support of many unions across Great Britain, including Unite, the largest labour union backing the party.

Johnson, writing in The Guardian, argues that Cooper presents the best chance to unite Labour in the post-Miliband era — and he makes much of the argument that Labour, founded in part on the principle of full suffrage for women, has the chance to elect its first female leader:

I’ve been enormously impressed by her poise, command of her brief as shadow home secretary, and her ideas on tackling inequality, child poverty and a radical programme of genuine devolution. She’s defended our economic record against the crass lies of those who suggest that Labour created the global financial meltdown; and she understands the crucial difference between pretending that the fiscal deficit can be ignored and planning to reduce it on a timescale that doesn’t choke off growth and hit the poorest hardest.

Johnson also takes some harsh shots at Corbyn and the ‘various far-left sects who last tried to bring their finger-jabbing intolerance into our party 35 years ago’:

Compared to former prime ministers Tony Blair and Gordon Brown, or to New Labour figures like Peter Mandelson, Johnson remains relatively popular among the Labour grassroots. The former leader of the Union of Communication Workers, Johnson once stocked shelves at Tesco and worked as a postman. A Marxist in his youth, Johnson entered the House of Commons as a MP in 1997 — the same year Blair rocketed to power — and he gradually worked his way up the leadership chain.

Beginning his ministerial career in 2001, he became work and pensions secretary in 2004, trade and industry secretary in 2005, education secretary in 2006, health secretary in 2007 and, finally, home secretary in 2009. There are more than a few Labourites who wish Johnson himself had contested the leadership, going back to the Brown era when it was so clear that Brown’s electoral chances in 2010 would be dismal.

Compared to Corbyn’s far-left supporters and Kendall’s staunchly Blairite supporters, Burnham and Cooper have positioned themselves precariously in the middle — a move that’s left both of them open to charges that they are overly cautious careerists with no core principles. Fair enough.

Johnson’s endorsement is a setback for Kendall — the most credible advocate of New Labour is not even backing the ‘New Labour’ candidate. It will put even more pressure on Kendall to stand down over the next 10 days.

But, most of all, it puts some definite light between Burnham and Cooper by bestowing the qualified stamp of Blairite approval on Cooper’s candidacy.

It’s a step that swings both ways.

It could make Cooper increasingly the consensus compromise candidate who really could unite the two wings of the Labour Party after September — and that’s bad news for Burnham. To the extent that Cooper and Burnham are competing for the same pool of Labour voters, Johnson’s endorsement could move first-preference (and, more importantly, if no candidate can win an outright majority on first preferences, for second-preference votes).

But it could also taint Cooper’s candidacy. To the extent Labour’s members really do want to turn left from New Labour, Johnson’s seal of approval could taint Cooper. It probably makes it a little more likely that Corbyn’s voters will list Burnham (and not Cooper) as their second choice. If the groundswell of projected support for Corbyn doesn’t materialize, his supporters’ second preferences will prove decisive in a showdown between Burnham and Cooper.

Fairly or not, Cooper is often lumped together with the populist economic views of her husband Ed Balls, the former shadow chancellor who lost his seat in the House of Commons in May, an unexpected and shocking result. An MP since 1997 from northern England, the 46-year-old Cooper was born in Scotland and has the support of Ian Murray, the sole Scottish Labour MP left in Parliament.

As shadow home secretary, in particular, she’s won admiration for standing up to home secretary Theresa May, and she’s emphasized women’s rights, and she advocated anti-stalking legislation and a governmental office for domestic violence. Though she’s sometimes flat on the campaign trail, and she lacks Balls’s fiery punch, it’s perhaps easiest to envision her, more than any of her three leadership competitors, as a future prime minister.