Professor John Curtice: Nine per cent swing would give Ed Miliband reason to cheer

It has all gone wrong for the Conservatives at the wrong moment. With much of the country voting in local elections on Thursday, support for the party in our latest poll of polls has slumped by three points.

At 33 per cent, the party is at its lowest ebb since the 2010 general election. Consequently, Labour can look forward to many a council gain, even though, at 40 per cent, the party's standing is unchanged.

Nearly all the seats being contested in England and Wales were last fought over in 2008, when Gordon Brown's government was unpopular and the Tories put in their best local election performance of the 2005-10 parliament. The latest figures represent a 9 per cent swing from Conservative to Labour.

If that swing is replicated on Thursday, Labour should not only gain control of the easy pickings (places where the party needs very little swing to seize power) together with those that represent a modest challenge, but also those at the top of its target list, where the swing required is at, or close to,nine per cent. A clean sweep of these would give the party good reason for celebration.

As well as winning seats from the Conservatives, Labour should also profit from the Liberal Democrats' woes. At 11 per cent, their latest poll reading is every bit as bad as it was a year ago, when the party recorded its worst local election performance since the 1970s.

If that setback is repeated, the Liberal Democrats will suffer a further erosion of the local-government base they have pain-stakingly built up over 40 years and which is a crucial foundation of many a seat they hold at Westminster. Such an outcome would do nothing to calm the unease among activists and MPs about the cost the party is paying for its role in the Coalition.

But there could still be a silver lining for the Tories – Boris Johnson remains ahead in the race for London Mayor. Meanwhile, Ed Miliband still has to worry about Scotland where further SNP gains are expected, though the nationalists may have set their sights too high in suggesting they could take control of Glasgow. In any event, expect the Tory spin doctors to seize whatever crumbs of comfort come their way.

John Curtice is Professor of Politics, Strathclyde University