I suppose, though, that he’d had a few minutes to get used to the idea when, on ITV’s General Election debate, Boris Johnson was the first to be openly derided.
I’m certainly not saying that Mr Corbyn looked comfortable but, when he uttered some palpable untruth, he must have been expecting the same treatment that the Prime Minister had just received moments earlier.
They were clearly rattled, though, and why wouldn’t they be for both of them rarely see and hear the ordinary, angry, scornful people that now inhabit our country.
The moment in the debate that made my toes curl (but nothing like as much as Messrs Corbyn’s and Johnson’s digits, I suspect) was when an unusually articulate member of the audience asked them why they should be trusted by the electorate.
Now, such a question should never need to be asked of our leaders, but neither should they be mocked on prime-time television.
Yet both are happening and both mark a dangerously low ebb in our national affairs.
The trust question is a veritable minefield for Mr Johnson, but he is Prime Minister and his opportunities for being tested on this point are many times greater than almost any other public figure.
Now, there’s a litany of ways that he can be seen as untrustworthy (just one, but the most obvious, being the breaking of his ‘die in a ditch’ Brexit pledge) but there’s something sinister lurking in the wings.
Ms Jennifer Acuri (one of the PM’s former associates) just happens to have dropped in from America and is trying to see her old pal right in the middle of an election campaign.
She’s had a couple of mild excursions with the media so far, but the real danger she poses is not the exposure of Mr Johnson’s already well known infidelity, but suggestions of murky financial dealings when he was Mayor of London. I suspect there’s more to come: she defines Boris Johnson’s untrustworthiness and she’s trouble with a capital T.
Meanwhile, Mr Corbyn is less colourful and just a simple, old-school Marxist. He’s already got his hands full with anti-Semitism, Brexit, the barmy Momentum movement and approval ratings that would make Mussolini wince, but none of those is worth a damn compared with his open support for terrorists and other sworn enemies of this country.
Former big cheeses in the intelligence services are telling us that he cannot be trusted with sensitive material; he mixes with and approves of people who have killed or want to kill Britons. How can he be trustworthy?
On last night’s Question Time election special in Sheffield, other leaders had a chance to show themselves to be more trustworthy than the unpalatable pair we saw battling in out last Tuesday – but, realistically, they are not in the frame to be Prime Minister.
And you could be excused for thinking that the result is already nailed on. It depends which poll you study, but it looks as though Boris Johnson’s lead over Labour is solidly in double figures and that he can expect a comfortable and workable majority that would enable him not to be dependent on the support of Northern Ireland’s DUP.
Fine, but if the election campaign is in its defining moments – as we’re told – it might be worth pausing to compare the similar period in the 2017 election. With three or so weeks to go, Theresa May had a bigger lead in the polls and her suitability to be Prime Minister was rated higher than Mr Johnson’s is now. And that ended well.
Talking of trustworthiness, after the pollsters’ abject failure to predict results accurately over the last several elections, no one but a fool would now depend upon them. But even if they give an idea of general themes, with the atmosphere now so febrile, everything will depend upon “events”. Remember how the last election was rocked by a rash of terrorist outrages? Well, the same could happen again, but a December election could decided by our capricious weather. Suppose a swathe of Scots cannot get to the polls due to snow or target seats in Yorkshire and the East Midlands get another wave of flooding. The Brexit imbroglio has made the electorate sick of politics and politicians: the slightest thing could upset any predictions.
But, if you’d like a forecast from me, it’s a depressing one. Further gaffes by the Tories and a crisis will erode their supposed lead and they will cross the line with a majority in single figures which will not be sustainable. Brexit will be delayed again and we’ll just stagnate: it will take another election to sort it all out.
Patrick Mercer is the former Conservative MP for Newark.