Now, after his impressive performance at the last general election, they see him as a realistic winner when Britain next goes to the polls.
Just the reverse has happened to Theresa May.
She was seen as a cool-headed, authoritative leader who would keep the Tories well ahead of Labour, and a racing certainty to win the next election.
Well, win she did, but in the process lost the Tories their overall majority in the House of Commons and put them in a far worse position than she was before she made her dreadful decision to go to the polls – a totally needless and, as it turned out, disastrous thing to have done.
So now Corbyn’s boot is on Theresa May’s foot, but added to all that, the Brexit negotiations are proving agonising, with a determined number of anti-Brexit Tories out to thwart them and posing a real threat to the Prime Minister.
But her woes do not end there.
A bunch of some 30 no less resolute Tory back-benchers are up in arms over the threat of yet more defence cuts.
They are led by two ex-military men, Johnny Mercer and Tobias Ellwood and have grimly warned May they mean business if Britain is stripped any further of its defences.
Now Gavin Williamson, the new Defence Secretary, is engaged in a fierce debate with Chancellor Philip Hammond, for more money to keep Britain’s defences relevant to current international threats and to ensure the would-be rebels do not strike a hugely damaging blow on the Government.
May is facing slings and arrows from all quarters while Corbyn sits there in relative harmony – a total reversal of roles.
These potentially trouble-making Tories do not seem to have the wit or common sense to realise that the more disaffection they publicly spread through the Conservative Party, the easier they are making it to get Corbyn a free pass to 10, Downing Street.
Will they never learn?
n Those who believed the curse of political corectness was just a passing phase, could not have been more wrong. As each day passes, its adherents seem to get ever more manic.
In pantomime for instance, a prince has been told he cannot kiss the Sleeping Beauty into wakefulnesss because it is not consensual and is therefore a bad example to childen.
Also, some teachers have been told not to greet their classes in the morning with, ‘Good morning, girls’ (or ‘boys’ as the case may be) but to use, instead, gender neutral words. And if you are in the Guides (formerly the Girl Guides I believe) and you insist on saying Grace at any point, you must avoid referring to Chistianity. Heaven forfend!
Plainly, I am nowhere near progressive enough for modern-day thinking.
n Headline in the Daily Mail on Saturday: “This was the week which convinced me Corbyn will never be PM.” Headline in The Times on the same day: “Corbyn’s Labour looks cynical enough to win.”
Take your pick, as they say.