George Eaton is political editor of the New Statesman.
The leader will be automatically included in the party's contest without nominations, senior figures say.
Senior party figures believe Labour's National Executive Committee could rule that the leader requires 50 MP/MEP nominations.
Theresa May's experience and the Conservatives' election rules make a victory for the Brexiter unlikely.
Labour MPs are now more likely to back her as "the unity candidate" against Jeremy Corbyn.
The Labour leader's supporters have framed the "corridor coup" as part of the "old politics" rejected last summer.
"I now apologise sincerely on behalf of my party for the disastrous decision to go to war in Iraq in March 2003," says the opposition leader after damning Chilcot report.
The Labour leader avoided mentioning Tony Blair but said there must be "consequences" for those who misled parliament.
Former PM sharply criticised for telling President Bush in July 2002 memo: "I will be with you, whatever".
Labour's deputy leader tells MPs that he will meet trade union leaders tomorrow to try and negotiate a settlement.
There is no agreement on whether the leader would make the ballot or whether Angela Eagle or Owen Smith would be the challenger.
The New Statesman goes behind the froth of daily headlines to look at the people and the passions shaping our world.
Be well-informed. Be a New Statesman reader.