IT WOULD seem Alex Salmond's fears about not being involved in the UK party leaders' TV debates have come true. Nick Clegg shines and gives his party a boost. Consequently, the SNP vote suffers.
Part of Salmond's concern is valid. Half of our YouGov poll was conducted shortly before Thursday's debate, half afterwards. Prior to the debate the Lib Dems were on 17 per cent in Westminster vote intentions north of the Border. Afterwards they were up six points to 23 per cent, thereby knocking the SNP from second place.
The Lib Dems may still not be riding as high in Scotland as they seem to be in England, but evidently their post-debate surge has percolated north of the Border too.
But Salmond would be wrong to lay the blame for all his woes on last Thursday's debate. Even before it, the nationalists were at just 20 per cent in voting intentions for May 6. Not only is this four points lower than the SNP tally in our last poll three weeks ago, but it is also the party's worst rating in any YouGov poll since their 2007 Holyrood victory.
The SNP bandwagon was already juddering to a halt even before Clegg pulled off his surprise.
Moreover, the Lib Dem advance in Scotland has not been at the SNP's expense. SNP support remained steady at 20 per cent after the debate was over. Rather it seems to have been Labour's vote that suffered – and it is to be presumed that Salmond will not be unhappy about that development.
But he will be unhappy that his party now clearly trails Labour in Holyrood voting intentions too. That was also true before Thursday. Apparently the SNP's honeymoon is now over and for the first time since 2007 there appears to be a real possibility that the SNP could crash to defeat in 2011.
Still, there is perhaps a more optimistic gloss that could be put on these findings. While the first leader debate, in particular, may not account for the SNP's fall in popularity, perhaps the broader fact that we are now in the midst of a Westminster election does do so.
The ever-present gap between the SNP's Westminster and Holyrood support demonstrates how support for the SNP can fall away when the public's attention is focused on UK-wide politics.
Even so, Salmond is still likely to be faced with the task of restoring his party's morale and appeal once the current Westminster contest is over and attention begins to focus on next year's Scottish Parliament election. And in the meantime he has to minimise the damage.
Perhaps it is time for him to reconsider his decision not to appear in the first Scottish leaders' debate on Tuesday. He might be mad at the broadcasters. But as Clegg has shown, a leaders' debate is certainly not an opportunity to be tossed away wantonly.
• John Curtice is professor of politics, Strathclyde University