In January next year, Alex Salmond will stand trial on multiple charges, including sexual assault and attempted rape. Even in the current bizarre world of politics, this is an extraordinary situation – the man was first minister of Scotland for seven years and has been one of the country’s leading figures for decades. Imagine if this were David Cameron or someone comparable.

Whichever way the trial goes, the consequences for the SNP are expected to be explosive. It has become received wisdom that Nicola Sturgeon is unlikely to survive the fallout.

“She’ll be gone by March,” a significant number of SNP politicians have confidently predicted to me. It has also become something of a mantra among her opponents. There have been rumours that, seeking a parachute, she has sounded out the UN about a job (which Sturgeon firmly denies). It would be unwise for legal reasons to explain why her “inevitable” departure has become such common currency, and I have no idea whether it is an outcome that is fated or not. But this is politics: the game is afoot, the drums are beating, and the likely contenders have begun to shake their tail feathers.

In the absence of the Salmond trial, Sturgeon would doubtless carry on unassailed. She has only been First Minister for five years and could easily serve another term at the top, and perhaps longer. She tends to divide opinion strongly in Scotland, but the Brexit imbroglio has cast her in a stateswoman-like role. She has seemed calm and principled as others have ripped up conventions and rules, or fallen foul of the highest courts, or come close to destroying their own parties. Yes, Sturgeon wants to break up the UK, but this is hardly a secret. In the past few years, compared to others, she has played with a relatively straight bat.

Yet events may undo her. It is at least thinkable that the SNP will go into the 2021 Scottish parliament election with a new face at the helm. And if it is thinkable, we should think about it — after all, it is entirely possible that the winner could take Scotland to independence within the next decade.

One safe bet: the transition will not run as smoothly as it did in 2014, when power passed from Salmond to Sturgeon without challenge. Sturgeon had long been the chosen one, the anointed heir, and the nationalists don’t like public scraps. The movement puts its holy goal of independence above personal ambition, and therefore largely avoids the public rows and splits that dog other parties. Personalities are not allowed to intrude.

But that was then. The SNP has changed significantly since its narrow loss in the independence referendum. It has many more MPs, for example, and a swollen party membership. A number of those energised by the 2014 campaign found themselves unexpectedly elected to parliament as support for the Nats soared in the referendum’s aftermath. Not all of them understand the SNP way of doing things, or were forged in the “band of brothers” era that bound people like Sturgeon, Salmond, John Swinney, Mike Russell and others so closely together.

The party is also more openly divided than it has been for some time. It is split on the issue of transsexual rights, for example — Sturgeon wants to make it easier for trans people to change their legally recognised gender, but has encountered stiff opposition from within the SNP, especially among prominent women. Equally, her cautious approach to the prospect of a second independence referendum — she is reluctant to hold one until she knows she will win it — has frustrated some. The Westminster group of MPs, especially, have shown a willingness to go against the grain.

So the battle to be the next leader of the party will not just be about who appears the pre-eminent candidate. It will also be about differing views on policy, positioning and strategy. Alternative approaches will be advanced and debated, in public — the SNP will show its workings. There are likely to be fall-outs and rows.

The current leadership’s favoured successor is said to be Derek Mackay, the Finance Secretary at Holyrood. Mackay is wily, able and energetic, and has overseen progressive changes to the Scottish tax system in recent years. He may, however, be seen as too close to Sturgeon.

The name Joanna Cherry is increasingly mentioned. The MP and QC has had a huge impact at Westminster, where she has led the campaign against Brexit and successfully taken the government to the Supreme Court over its unlawful proroguing of parliament. Cherry is whip smart, ambitious, and sure of herself, and is one of those who has spoken out on transgender rights. She is, however, close to Salmond and her combative nature has attracted internal criticism, but her star is in the ascendant.

Among the old guard, John Swinney, the former party leader who is Sturgeon’s deputy, is talked of as a potential caretaker first minister if Sturgeon falls on her sword. Swinney is well-liked across politics, and an experienced minister and party organiser. He is unlikely to want the job full-time, but could step in to steady the ship for a while. Mike Russell, the Scottish government’s constitution minister, another old ally of Salmond’s, may fancy his chances, but has the kind of personality that strongly divides internal opinion.

It’s worth watching Angus Robertson, the party’s impressive former Westminster leader who unexpectedly lost his seat in the 2017 general election. Robertson has been biding his time, and looks set to stand for an Edinburgh constituency in 2021. He has already shown he has what it takes, has only just turned 50, has a big brain, and does not lack ambition.

Others might fancy their chances too: Alyn Smith, a respected MEP, has found his voice during the Brexit debate and is looking for a Westminster seat ahead of the next general election. Kate Forbes, Sturgeon’s digital economy minister, is the pick of the young Turks: a Cambridge graduate, she has intellectual capacity coupled with a winning personality, and would represent a genuine change of the guard. It may be too soon for her, however.

There are still more. It seems clear that when the time comes — whether next March, after 2021, or in a decade’s time — there will be a fight not just for the top job, but for the soul of the SNP. Fights for the soul are usually brutal, messy and damaging, as Labour and the Tories are showing us. In that sense, the Nats are just like everyone else.