Boris Johnson could step in to “save” the Tories from Nigel Farage as the party is defeated at the General Election, according to his biographer.
Andrew Gimson said friends say he has “not given up thoughts of a comeback”.
Writing in Conservative Home, Mr Gimson said: “If, as the opinion polls suggest, Rishi Sunak leads the Conservatives to a shattering defeat, its magnitude increased by Nigel Farage's success as the leader of Reform UK in attracting Tory votes, Johnson will step forward as the one person who can save the party from the opportunistic takeover bid which Farage will then launch.
“As Johnson's biographer, I have to say it would be out of character for him not to do this.”
Mr Gimson said “something of the sort happened” in 2019 when Mr Johnson took over from Theresa May in the wake of the Brexit Party's landslide victory in the European elections.
He added: “Johnson stepped forward as the one man who could save the Conservative Party.
“He beat off stiff competition from (in order of elimination) Rory Stewart, Sajid Javid, Michael Gove and Jeremy Hunt, in November 2019 forced Farage to stand down Brexit Party candidates in the 317 seats already held by the Conservatives, and in December led the party to its greatest general election victory since 1987.
“He did this as an insurgent, a candidate for whom people could vote in order to express their discontent with the state of things, and in particular with May's failure to get Brexit done.
“One of the difficulties experienced by Sunak in this election is that he has no affinity with disaffected voters. Nor did May. Nor indeed does Sir Keir Starmer.”
Mr Johnson was forced out of No 10 in summer 2022 following a series of scandals including partygate.
But there has been ongoing speculation over whether he will make a return to frontline politics.
It comes as Mr Farage, who made a comeback as Reform's leader earlier this month, has outlined plans to mount a reverse takeover of the Conservative Party to form a new centre-right grouping.
The Brexit architect has suggested his political model is Canada's Stephen Harper, who orchestrated a merger between Reform and their Conservative rivals to unite the right.
A YouGov poll last week put the insurgent party one point ahead of the Tories for the first time.