Boris Johnson is apparently 'taking soundings' from friends on whether to stand in next week's contest to succeed Liz Truss.
The former prime minister believes it is a matter of 'national interest', according to reports in The Times.
Johnson only left office six weeks ago - but is believed to be consulting allies on whether he should run again, after Truss resigned earlier this afternoon.
Speaking from a lectern in Downing Street, Ms Truss said she had told the King she was resigning as the leader of the Conservative Party as she recognised she “cannot deliver the mandate” which Tory members gave her little over six weeks ago.
She held talks with the chairman of the 1922 Committee of backbench Conservatives Sir Graham Brady and agreed to a fresh leadership election “to be completed within the next week”.
“This will ensure that we remain on a path to deliver our fiscal plan and maintain our country’s economic stability and national security,” she added, as she was accompanied by husband Hugh O’Leary.
“I will remain as Prime Minister until a successor has been chosen.”
Ms Truss’s resignation came just a little over 24 hours after she told MPs she was “a fighter, not a quitter”.
But her odds of survival were slashed after chaotic scenes in the Commons followed the resignation of Suella Braverman as home secretary.
The number of Tory MPs publicly demanding Ms Truss’s resignation doubled before lunch was over on Thursday, taking the total to 15, but a far greater number were privately agitating for her exit.
The mechanism of how the next leader – and Prime Minister – will be chosen was unclear.
Allies of Jeremy Hunt, the new Chancellor brought in to shore up the economy and Ms Truss’s premiership after chaos on the financial markets, said he would not be standing.
The pound lifted on the resignation announcement following another volatile 24 hours for the currency amid political turmoil.
Liberal Democrat leader Sir Ed Davey said: “We don’t need another Conservative Prime Minister lurching from crisis to crisis.
“We need a General Election now and the Conservatives out of power.”
Ms Truss had summoned Sir Graham to Downing Street for a hastily-arranged meeting on Thursday morning, with sources saying she was “taking the temperature” of the Tory party.
What Sir Graham told her was unclear, but she was left realising her time was up. “The statement was the result” of their conversations, a source confirmed.
Ms Truss’s 44 days in office falls months behind the next shortest premiership of Tory statesman George Canning, who spent 118 full days as PM in 1827 before dying in office.