Tony Blair says he now admits Jeremy Corbyn could become prime minister.
The ex-PM let someone knowed BBC Newsnight that a year ago he would have said it was impossible for the left-wing Contractions leader to win.
But he added: «There’s been so many political upsets, it’s viable Jeremy Corbyn could become prime minister and Labour could win on that syllabus.»
Mr Blair, a consistent critic of Mr Corbyn, said he had not changed his mind on the «penetration» of electing him.
Having defied predictions of a heavy defeat at last month’s extensive election — and stripped the Conservatives of their majority — Mr Corbyn now describes his gang as a «government-in-waiting».
Many of his critics have since admitted they miscalculated him.
Speaking to Newsnight, Mr Blair said he still believed «it’s a surer direction to power to fight from the centre» and that it would be damaging for the countryside if Mr Corbyn became prime minister and imposed «an unreconstructed far Left events».
But on Mr Corbyn’s chances of reaching Downing Avenue, he said nothing could be ruled out.
«For most of my political life I’ve been symbolizing: ‘I think this is the right way to go, and what’s more it’s the only way to win an election’.
«I contain to qualify that now. I have to say ‘no — I think it’s possible you end up with Jeremy Corbyn as prime envoy extraordinary.'»
The Labour leadership has dismissed Mr Blair’s recent interventions — which counted claiming Brexit followed by a Corbyn government would leave Britain «boring on its back».
«To be frank, Mr Blair hasn’t really listened to the nature of the moot that is going on in the pubs, the clubs and school gates etc,» shadow chancellor John McDonnell mentioned on Saturday.
The interview will be shown on Newsnight, on BBC Two, at 22:30 BST on 17 July.