The irony is that just four months ago the message was king.
The endless repetitions of "strong and stable" seemed to leave little room for prime ministerial personality and warmth – so much so that delegates on my media training courses have since asked whether it is even possible, as a spokesperson, to communicate your key message while still being an authentic human being.
Well, of course it’s possible.
Just because May herself hasn’t yet managed to do both (partly due to bad luck – anyone can get a cold), it doesn’t mean that doing the two things at once is unachievable.
And he’s not the only one.
Across the Atlantic, and the political divide, Donald Trump pulled off exactly the same trick in the Presidential election last year.
Like Corbyn, he was the underdog. But a sufficient number of voters were inspired by Trump's key message, 'make America great again', and clearly enough of them were prepared to support a flawed man, who "at least says what he thinks".
By contrast, Hilary Clinton struggled to convey authenticity and warmth. And does anyone remember what her campaign message was? Me neither.
Some might be thinking "But I can’t stand Jeremy Corbyn", or "Donald Trump is my worst nightmare".
And that’s one of the difficulties of being authentic – not everyone will like what they see.
But far better in the long run to be true to yourself and your message than to attempt to iron out every wrinkle and imperfection in an effort to please everyone.
So what about May? If you look at the text of her speech in Manchester, as opposed to the excruciating video, you’ll see that she is at last revealing more of herself and her life story, and linking it to what she called "the British Dream" – which was surely the headline she was hoping for.
It might all be too late, and who knows how long she can hold on for. But at least the Prime Minister is now striving for a healthier balance between message and messenger.
Robert Taylor is a media and comms trainer