"Even Charlie is going to have to watch himself" came the warning from a long standing Highland Lib Dem.

It was the first indication from Charles Kennedy's Ross Skye and Lochaber seat that even the former party leader could fall in the face of the SNP swing.

That was a few weeks ago, then came Lord Ashcroft polls this week which did more than confirm local party fears. They predicted a 21.5% swing from Lib Dem to the SNP, more than enough to take the seat.

Most had assumed that with a remarkable 52.6% share of the vote and a majority in excess of 13,000 in 2010, Charles Kennedy would be able to withstand the SNP surge. The Lib Dems' thinking had always been that the local popularity of their incumbent MPs would be enough, particularly in their Highland heartland. But apparently not even Kennedy's hitherto sustained popularity would be sufficient if these polling figures are replicated on May 7.

The Highlands with Orkney and Shetland have long formed the party's largest area of continuous Westminster seats. It stretches northwards from the Mull of Kintyre in the south of Argyll all the way to Muckle Flugga and the Shetland island of Unst. Now it looks as though Alistair Carmichael on the other side of the Pentland Firth may be the only one left.

Of course things might yet turn out differently. Anyone who has seen Charles Kennedy at meetings in village halls in the small communities of his far flung constituency, will have recognised his sheer genius at just appearing ordinary; one of us; a thoroughly reasonable and decent guy; somebody people are happy to leave as their representative in Westminster.

His measured treatment of party political rivals also goes down well with the many who are so tired of aggression for aggression's sake.

Even at the time of all the publicity surrounding how his drinking was affecting his leadership of the party, most constituents from Skye to the Black Isle, remained loyal. It is an area that knows all too well about problem drinking, and many felt sympathy for their MP.

He also has distanced himself from the coalition government, unlike his party colleague and near neighbour Danny Alexander. He knew all too well how that would play in the Highlands; the sense of betrayal amongst many Lib Dem voters seeing their ballot papers support a Tory led government, despite Danny's successes on the likes of rural fuel and Crown Estate monies for coastal communities.

However there has been growing feeling in the seat that CK has not been as assiduous recently as he should be.

It is something his able Skye-based SNP rival is trying to exploit. In particular Kennedy's 30% voting record in the House of Commons since 2010 has become an issue. Ian Blackford, a former managing director of Deutsche Bank AG, who was previously the SNP's national treasurer even launched a 'Where's Charlie?' Twitter hashtag.

Mr Blackford is a good communicator who has been active in local campaigning on such issues as the return of air services to the island, and with his background in finance is clearly well placed to surf the remarkable current wave of SNP support. But beating Charlie Kennedy was almost unimaginable just a short while ago. That is now a distinct possibility, which has stunned the party.

Of course Kennedy might well get some voters back yet.

He has started to mix it with the Ministry of Defence over plans to double the size of the submarine testing range between Raasay and Applecross, impacting on local fishermen. Fighting on such local issues like plays well with voters. But he obviously is going to have to do more.

The problem is that the Lib Dems don't really know how to get out of the SNP headlights. But neither do Labour apart from holding that every vote for the SNP helps David Cameron stay in Downing Street. Lord Ashcroft's polls show that is not working so far.

The truth is that nobody really knows what is happening amongst the Scottish electorate. Various theories have been advanced, but none really fully explain the size of the SNP surge. It is clear that the Scottish people want to see things done differently, that the normal Westminster service should not be resumed now the independence referendum is out of the way.

It is also clear that this is as true north of the Highland Line as south of it.