Editor's Note: (Jane Merrick is a British political journalist and former political editor of the Independent on Sunday newspaper. The opinions expressed in this commentary are hers.)
London(CNN) One year ago this week, Theresa May delivered a memorably disastrous speech to her party's annual conference that was a metaphor for her struggling premiership: a heckler handed her the British equivalent of a pink slip, she battled with a persistent cough as she tried to speak, and parts of the set fell apart behind her.
But the UK Prime Minister may be feeling wistful about last year's accident-prone event when she considers that, thanks to the chaos over Brexit, this conference threatens to be worse -- and could even be her last as leader.
At the four-day gathering in Birmingham, May will try to reassert her authority over her party, claiming that she is the only person who can deliver Brexit.
The PM will say she alone is the one who has a coherent plan for the UK's withdrawal from the European Union, which doesn't impose a hard border between Northern Ireland and the Republic of Ireland, but also allows the country to trade as freely as possible with both Europe and the rest of the world.
This plan, known as Chequers after her country residence where it was approved by the Cabinet in July, is opposed by all factions in her Conservative Party and was rebuffed by EU leaders in Salzburg earlier this month. May has insisted there is no alternative to Chequers -- it is either this deal, or none at all.
Up steps, once again, Boris Johnson, who has an annual habit of trying to make the Conservative conference about him more than his leader. Johnson resigned as foreign secretary in July in protest at Chequers, and wants Britain to pursue a Brexit with fewer ties to the EU.
On Friday, he penned a 5,000 word article setting out his alternative plan, calling it "Super Canada," a model based on that country's free trade agreement with the EU. Chequers, he wrote makes the "intellectual error of believing we can be half-in, half out" of the EU.
"Super Canada" would mean zero tariffs and zero quotas on all imports and exports between the UK and EU and mutual recognition agreements to ensure standards. By necessity, there would need to be a border in Ireland, the new physical frontline between the UK and the EU -- something which Chequers avoids.
Johnson insists this would not mean a hard border -- but, using technology, the "extra procedures" necessary would be carried out away from the politically sensitive divide between the two countries.
The intervention by Johnson is designed to ramp up pressure on the Prime Minister to ditch Chequers in favour of a harder Brexit formulation that many in her party want. It is also a scene-setter to portray him, to the Tory party in Birmingham this week, as a leader-in-waiting.
Many Tory MPs -- some of whom are former allies of May and not arch-Brexiteers -- have openly discussed her handing over power once Brexit takes place on March 29 next year. Johnson is desperate to be regarded as the Brexiteers' choice for the next leader, but there are many MPs who are opposed to him, and would even leave the Conservative Party should he become Prime Minister.
The conference is taking place, therefore, with May's party at the most divided and fractious it has been for years. By contrast, the opposition Labour Party has just finished its own conference, in Liverpool, having reached a relative point of unity over Brexit.
Labour's leader, Jeremy Corbyn, has been effectively sitting on the sidelines for more than two years over Brexit, and deliberately so: holding an ambiguous position has alienated neither Labour supporters who voted leave nor remain.
Yet last week, Corbyn stepped into the Brexit debate as he has never done before. He laid out conditions for May's proposed deal with Brussels, and said if she couldn't meet them there should be a general election.
The technicalities of a further unscheduled national vote -- after last year's disastrous snap election when May lost her party's overall Commons majority -- mean this is unlikely to happen.
But Corbyn's intervention, during a week in which left-wing populist measures were also floated by Labour, makes clear he is now ready to do battle with the Prime Minister over Brexit.
Whatever Brexit deal May reaches in November with Brussels negotiators, if there is a deal at all, it is likely to be opposed by the Labour Party in parliament, making a vote of no confidence, and subsequently another election or a second referendum on EU withdrawal, all the more likely.
In Birmingham this coming week, May has little choice but to hold her ground. Until now, she has been fortunate that her opponents have lacked direction over Brexit. But events can unfold quickly at party conferences, and she needs to show authority if she is to ensure it is not her last.