ALMOST nothing can be said about the criminal charges facing Alex Salmond, but it is a fair assumption his arrest is not a boost to the independence cause.

Nicola Sturgeon’s ideal backdrop for her imminent announcement on the timetable for indyref2 is not difficult to imagine. Growing support in the polls. A bit of political momentum. And nothing disastrous lurking around the corner.

A potential trial involving her predecessor and mentor, who has been charged with multiple counts of attempted rape and indecent assault, hardly meets the criteria and will inevitably provide the SNP leadership with sleepless nights.

But the impact of the Salmond case on Scotland’s constitutional future should not be over-stated. The former SNP leader is a political has-been who took an axe to his own reputation when he agreed to work for a Putin propaganda station. His supporters are not swing voters; they will back Yes regardless of the facts.

Sturgeon faces referendum roadblocks far more formidable than the Salmond case, particularly over her delay in revamping the case for independence and, critically, explaining the process by which she intends to deliver another plebiscite.

The First Minister’s line has been to claim she has a “cast iron” mandate for a referendum. A combination of her party’s victory at the last Holyrood election, Parliament endorsing a second vote, as well the SNP winning a majority of MPs in 2017, turned it into a “triple lock” mandate.

However, a "mandate” is a rhetorical device that has no basis in law. In politics, the only mandate a party can secure from voters is the right to bring forward a policy for parliamentary scrutiny. An initiative may be pushed through, rejected, or tweaked, but there is no such thing as automatic implementation based on an election victory.

A mandate must also reflect the powers of the legislature. The SNP could win the next Holyrood election on the basis of demanding a £10bn funding top up from Westminster, but Theresa May would be under no obligation to hand over the money. You cannot force another Government to do something.

Which brings us to indyref2. The first referendum became a reality after the UK Government handed the Scottish Parliament, via the Edinburgh Agreement, the temporary power to stage a vote on independence. Holyrood can only have a “mandate” to request this power again, rather than having a guaranteed right to another referendum. The cast iron is more akin to soggy paper.

Let us suspend reality and pretend Holyrood does have the power to organise another referendum unilaterally. In 2016, 63 SNP MSPs - a minority - were elected on the basis that the Parliament should have this “right” if there was a “material change” such as “Scotland being taken out the EU against our will.”

However, the pro-independence Scottish Green MSPs did not sign up to this form of words ahead of the poll. Patrick Harvie’s party instead suggested indyref2 should be triggered by a petition being signed by an “appropriate number of voters”. This has not happened. Only by ignoring the Green manifesto and pretending they made the same commitment as the Nationalists can you conjure a credible majority at Holyrood.

Some of the more adventurous Nationalists would like Holyrood to ignore Westminster and legislate for a Catalonia-style referendum. But anyone with a basic understanding of Sturgeon’s cautious political instincts understands this will not happen. She has no ambitions to become Scotland’s Clara Ponsati.

The importance of the Edinburgh Agreement, which Sturgeon helped draw up, was not whether such a bilateral deal was legally required. What it confirmed was that a legitimate referendum must be based on the consent of both sides. Without such a partnership you are left with a “wildcat” referendum, legal challenges and a boycott from the No side. No sensible person in the Yes movement would favour this move.

Sturgeon also faces the problem of an increasingly restless pro-independence movement. A senior Yesser told me two groups currently co-exist in the “indy” coalition. “You have activists whose priority, above all else, is to have another independence referendum,” he said. “But you have wiser heads whose priority is to win a referendum.”

A primary reason behind Yes losing in 2014 was the inability of the pro-independence side to reach out to soft No voters and speak their political language. Some activists made no attempt; others were simply contemptuous of their opponents.

I attended Yes events during the campaign for news-gathering purposes and my notebooks are littered with examples of aggressive speeches and contributions that persuaded nobody.

Here are a selection of the descriptions by speakers and audience members on the UK: “war-mongering”; “economically bankrupt”; and “failed imperial state”. Labour supporters were dismissed as “red Tories” and the BBC was either “biased” or a “disgrace”.

Some of the hustings were open-mic, rather than open mind, and marked by apocalyptic warnings that only appealed to people who were already furious. Nuance was a foreign country and subtlety a stranger. Many of the same folk are now demanding Sturgeon immediately delivers indyref2.

The First Minister knows, deep down, there is only one narrow road that can take her to a second referendum. The SNP and the Greens would need to win a majority of seats in 2021 on an explicit promise of another vote. Such an outcome would not constitute a “mandate”, but it would put maximum pressure on the UK Government. Legal solutions have a habit of following political victories.