A WHITE Mercedes draws up outside Holyrood and two detectives leap out. They arrest the leader of the Scottish Labour Party, Wendy Alexander, and bundle her off to the station to be charged under the Political Parties Act 2000. Officers raid her family home in Glasgow and question her husband Professor Brian Ashcroft for several hours, even rifling through his underwear.

Well, you may laugh. But if the police are able to arrest Tommy Sheridan for alleged perjury, and raid his home, then who is to say they won't do the same to Alexander for accepting an illegal donation? No-one expects it to happen, of course, because Alexander is under the protection of Gordon Brown, the prime minister. But stranger things have been known. During the cash for honours investigation, a number of Tony Blair's closest Number 10 aides were arrested, in Ruth Turner's case after a dramatic dawn raid.

With the Electoral Commission now expected to report on the donations affair in the new year, it looks like Scottish Labour's nightmare is set to continue. Alexander's main contribution to Scottish politics in 2007 should have been her bold initiative to extend the powers of the Scottish parliament. Instead she has been mired in controversy over dodgy donations.

Most people accept her word that she didn't know she was breaking the law by allowing her leadership campaign to accept an illegal donation from the tax-exile, Paul Green. Unfortunately, under the act, that isn't really a defence. And for as long as the question of illegality hangs over her leadership, she is severely handicapped at first minister's question time. Any attempt to hold Alex Salmond to account over questions of probity - such as his relations with Donald Trump - would immediately rebound upon her.

Team Wendy expects this cloud to shift in the new year, but no-one is sure it will. At the very least, she has lost valuable time in establishing herself as a credible opposition to Alex Salmond. Even as the Nationalists' honeymoon wears off, Labour remains enfeebled. The SNP polling figures are off the scale, and support for independence is growing. If she doesn't recover, Alexander may be sacrificed to atone for Labour's fund-raising sins north and south of the Border.

And questions remain about her personal popularity - even within her own party. To lose one spin doctor is unfortunate, but to lose two - Brian Lironi and Matthew Marr - in the space of as many months, looks like carelessness. Alexander's detractors are saying that she remains headstrong and demanding, and recall that a senior civil servant, Andrew Baird, refused to work with her when she was enterprise minister six years ago. That all ended in tears when Alexander arrived on Jack McConnell's doorstep at 6am, with her resignation letter in hand.

Wendy Alexander has many strengths and, as Labour's first woman leader, she probably represented its best chance of renewing itself. She has shown resolve and staying power, but you will find few commentators putting money on her surviving 2008.