Jeremy Corbyn is dominating the Labour leadership race in the polls and in the speeches his rivals make. Yvette Cooper this morning (13 August) attacked the left-winger and claimed she was the real "radical alternative" in the contest, citing her economic "credibility" and vision for a capitalism that "serves people".

The Manchester speech pushed former favourite Andy Burnham into action. The Leigh MP took to the airwaves on 13 August to criticise Cooper for "misreading the mood of the party" by "just attacking people and making dire warnings". Burnham is in competition with Cooper, a former work and pensions secretary, to become Labour's so-called "anyone but Corbyn" candidate.

The latest poll from YouGov, which questioned more than 1,000 Labour supporters and was commissioned by The Times, estimated that Burnham was ahead of Cooper (21% vs 18%). But the bad news for the former health secretary was Corbyn had a 32-point lead over him on first preference votes (53% vs 21%).

The race is beginning to pick up as registrations closed yesterday (12 August), with more than 610,000 people signing-up to vote in the contest. The first ballots will be sent out tomorrow (14 August). Burnham, as the vote looms, appeared on the BBC Radio 4's World At One this afternoon.

Trident renewal for Burnham

The 45-year-old, besides attacking Cooper, confirmed he would renew the UK's nuclear deterrent, Trident. The policy outlines a clear difference between Corbyn, who has promised to scrap the programme, and Burnham. The Leigh MP has seemingly moved to the left since Corbyn entered the race after the veteran parliamentarian drew lots of support for his socialist agenda.

Burnham recently promised, for instance, to renationalise Britain's railways "line by line". He told the Daily Mirror: "We need a new approach to our railways, one that puts passengers before profit. That's why I will work to bring the railways back under public control and public ownership.

"Under my leadership, Labour will ensure there is proper and accountable public control of the railways, with passengers' interests put first – an end to the fragmentation and privatisation."

The Labour leadership contest will conclude when Ed Miliband's successor is announced at a special conference on 12 September. Tony Blair, one of the party's most successful leaders, has warned a Corbyn victory could "annihilate" Labour. He wrote in The Guardian: "If Jeremy Corbyn becomes leader it won't be a defeat like 1983 or 2015 at the next election. It will mean rout, possibly annihilation.

"If he wins the leadership, the public will at first be amused, bemused and even intrigued. But as the years roll on, as Tory policies bite and the need for an effective opposition mounts – and oppositions are only effective if they stand a hope of winning – the public mood will turn to anger."