The Labour leader is set to make a leaders’ debate even more important tonight.
For political obsessives like candidates, advisers, members and, yes, journalists, there is nothing quite like a bit of late-stage drama to inject life into an election campaign.
And so it proved today, when, with just a week of campaigning left, Labour leader Jeremy Corbyn announced he would take part in a leaders debate being hosted by the BBC.
It is a direct challenge to Theresa May, who has avoided even the suggestion of a leaders’ debate so far, and Mr Corbyn had previously stated he wouldn’t join a debate without the Prime Minister.
Now, however, with the polls seemingly tightening (though still showing a significant Tory lead) Mr Corbyn has decided to seize the initiative by appearing on tonight’s debate in Cambridge.
We look at the format for tonight’s debate, what to expect, and what impact (if any)it will have on the election on June 8.
An (almost) leaders’ debate
In British politics, few things are ever straightforward, so tonight’s leaders’ debate won’t be a leaders’ debate in the strictest sense of the word.
The seven-way debate won’t actually feature the leaders of the seven main parties represented at Westminster, even before accounting for the absence of Theresa May.
Lib Dem leader Tim Farron and UKIP’s Paul Nuttall will join Mr Corbyn, as will ‘co-leader- of the Greens, Caroline Lucas, and Amber Rudd will stand in for Mrs May.
Leanne Wood will represent Plaid Cymru, and, despite being an old hand at telivised debates, Scotland’s First Minister won’t take part.
Officially, the SNP say that as is this is a Westmisnter debate, their Westminster leader should take part, and so Angus Robertson steps in.
Not being an MP hasn’t stopped Leanne Wood or Paul Nuttall, nor has it stopped Nicola Sturgeon from taking part in other debates.
Angus Robertson has equipped himself well at Prime Miniserts Questions, so is a natural fight for the debate, although getting a profile boost while he attempts to hold of a strong Tory challenge in his own constituency is no bad thing.
What to look out for
The debate which had Ed Miliband alongside his fellow ‘non-incumbent’ leaders in 2015 (everyone bar Nick Clegg and David Cameron) was considered a mistake after the fact by his advisers.
Rather than looking like the only potential Prime Minister on a stage of no-hopers, he was instead criticised from left and right and ended up looking weaker.
That’s the line that Jeremy Corbyn has to tread, although he will be buoyed by a strong performance in Monday’s clash with Jeremy Paxman.
Watch out for all participants bar Amber Rudd criticising Theresa May for not turning up (presuming the Prime Minister doesn’t shock us all by U-turning).
Ms Rudd herself has almost an impossible job to do. She will have to appear more competent than Mr Corbyn, though not Prime Ministerial as such, as she will be lauding the absent Mrs May’s leadership skills.
With whispers abound of Amber Rudd as a potential successor to the Prime Minister, she must be careful not to perform too well, lest the Team May attack dogs start to see her as a threat and brief against her.
Perform poorly, and that briefing will still take place, though for different reasons.
For his part, Mr Robertson will try and appear measured and statesmanlike as he puts forward the SNP’s message of friendship across the UK, though with an undeniable focus.
He’ll likely be first to seize on any anti-immigrant rhetoric from UKIP’s Paul Nuttall, which could make for a fiery clash.
Will it make a difference?
Though the concept of TV debates is a relatively new one, the evidence suggests that a single debate won’t affect the outcome of an entire election.
They can help shape narratives however, and if some of the opposition parties can land blows by commenting on Mrs May’s absence, it can reinforce the notion that the Prime Minister is cautious too a fault.
If she is deemed ‘running scared’ by a Labour leader who has enjoyed improved approval ratings, Mrs May and her party may well amp up their personal attacks on Jeremy Corbyn.
That can be highly effective, though could potentially backfire.
Unless there is a massive gaffe by one of the two main party representatives tonight, then the debate will likely give only two day’s worth of headlines.
In our fast moving news cycle, that’s a relatively short space of time.
But make no mistake, for all the politicians, and not least the Prime Minister, tonight’s debate is fraught with danger.