ITV News Political Editor Robert Peston believes only Boris Johnson or David Davis are "credible candidates" to replace Theresa May as Conservative party leader.
He said: "I don't think it's an absolute certainty that [Theresa May's] going, though I think it is pretty likely.
"The reason I rule out Amber Rudd - who many people have been speculating as a possible future leader - is that if she wins her seat, she would have the narrowest of margins of victory.
"You simply can't appoint - as leader of your party - somebody who you can't be confident would keep their seat in a subsequent General Election in just a few months".
* Amber Rudd later held her seat by 346 votes.
Theresa May is expected to receive a frosty reception when she meets the 1922 Committee later. But what do we know about the group?
The Prime Minister appointed her former leadership rival as Environment Secretary as she confirms her new top team.
He insisted he would be backing Theresa May as leader and has warned MPs to "calm down and get behind the Prime Minister".