Both Andy Burnham and Yvette Cooper’s campaigns are today claiming their candidate is best placed to beat Jeremy Corbyn in the Labour leadership race, as ballot papers begin to drop today. The row comes as this morning’s Telegraph reports that Peter Mandelson tried to convince Burnham, Cooper and Kendall to stand down and stop the election.

Yesterday, Yvette Cooper supporter Liam Byrne published a blogpost claiming that their canvassing returns showed Cooper in second place, and picking up two-thirds of Burnham’s second preferences – giving her the best chance of nudging ahead of Corbyn in the final round.

He wrote:

“A massive 66% of Andy Burnham supporters said they were giving their second preference to Yvette. Just a tiny 13% said they planned to second preference Jeremy or Liz.

What does that mean? It’s simple. When Andy goes out, the overwhelming share of his vote goes to Yvette – putting her clearly on course to beat Jeremy in the final round.

The conclusion: as much as I welcome the way Jeremy has shaken up the policy debate, only Yvette can really best him to become Labour leader – and our next Labour Prime Minister.”

However, these figures are not backed up by last week’s YouGov poll, nor the internal data from the Burnham or Kendall camps. Sources in both camps say that while the second preferences of Cooper voters overwhelmingly go to Burnham, many of Burnham’s transfer to Corbyn. This means that if Burnham were knocked out before Cooper, Corbyn would have a greater chance of victory.

The Telegraph splash says Lord Mandelson appealed to the three non-Corbyn candidates to form a pact and simultaneously pull out of the race, forcing the election to be called off. However, this plan was supposedly put on ice after it became clear it would hand victory to Corbyn. The paper also reports that Liz Kendall personally spoke to Yvette Cooper about standing down to unite behind Burnham as the anti-Corbyn candidate, but Cooper declined. A source in Kendall’s campaign vigorously denied the reports.