E VEN AS IT enters its 12th year in government the Scottish National Party remains popular. Despite the trials of office and the efforts of opposition parties to sink the nationalist project, the SNP has sailed serenely on, polling around 40% while the Conservatives and Labour scrap it out in the 20s. At around the same point in its life-cycle the New Labour government, that other election-winning behemoth, was sometimes slipping into third behind the Lib Dems.

But the SNP’ s smooth progress has hit an iceberg. On January 24th Alex Salmond, the party’s 64-year-old former leader, who from 2007 to 2014 was Scotland’s first minister, was charged with nine sexual assaults, two attempted rapes, two indecent assaults and one breach of the peace. He denies them all.

Mr Salmond is the most important figure in the SNP’ s history. He took the party into government and led it to an unexpectedly close 55%-45% defeat in the independence referendum of 2014. His successor as leader and first minister, Nicola Sturgeon, has long described him as her mentor and friend.

That relationship now looks wrecked. When two female civil servants made allegations against Mr Salmond last year, the Scottish government began an investigation, after which the police were called in. Mr Salmond is said to feel betrayed by his protégée; Ms Sturgeon’s aides accuse his team of smearing her.

The wider consequences could be significant. Ms Sturgeon insists her timetable for calling another independence referendum is unchanged, and that she will set out her plans before Brexit, due on March 29th. But it is hard to see how the SNP could mount an independence campaign with the charges against Mr Salmond in the air. Much depends on the outcome of his case.

Further, Ms Sturgeon is herself in hot water. She had five private conversations with Mr Salmond during her government’s investigation, including two at her home. It took her two months to report them to civil servants. An inquiry is considering whether she breached the ministerial code. More may follow.