The latest poll of polls puts Labour on 31%, 16 points behind the Tories who could win around 390 seats on June 8.
But Stephan Shakespeare, chief executive of polling firm YouGov, said those within Labour who blamed Corbyn for its bad polling should not dismiss him or his movement, given the support he had among younger people.
“Important sections of the electorate really like [Corbyn], and feel he speaks for them,” he wrote in The Evening Standard.
“One of these groups is the young — Corbyn leads easily among the under-25s not just on policy but on ‘best prime minister’.
“If the election were held only among the under-fifties, Corbyn could beat May.”
Every poll of the election has given the Tories a commanding lead but a YouGov poll for the Times on Thursday put Labour on 32%, its highest of the campaign so far but still way behind the Tories.
Corbyn’s allies are reportedly pushing for him to remain leader if Labour matches the 30.4% of the vote it achieved under Ed Miliband in 2015.
Shakespeare wrote that none of his company’s polling finds “shakes the near-certainty of a Tory victory”.
But he warned a defeated Labour it could be even worse off if it overthrew Corbyn without a clear idea of how to replace his mission.
“Scorning Corbyn and his supporters could be perilous, because voter groups who feel marginalised have shown themselves capable of flexing their muscles and ending up on top,” he wrote.
“If Labour after this election ejects not only Corbyn but his mission, without a clear idea of embracing both the centre of politics and the frustrated margins, they could be even worse off.
“Party loyalties across the spectrum are weaker than ever, and there is no security for any of them.”