John Curtice: Labour has little to lose in this poll

It might be thought that Labour's latest plunge in the opinion polls means the party is heading for serious losses in this year's local elections on1 May. However, there is one good reason why that is unlikely to happen – Labour did so badly when most of the seats being contested this year were last up for grabs in 2004.

Held on the same day as the European elections, the 2004 local elections saw Labour record its worst local election performance since at least the 1960s. It lost nearly 500 councillors.

There was just one striking exception to that dismal story – Ken Livingstone's re-election as London Mayor. Thanks to his personal popularity, Mr Livingstone won even though his party was being outpolled in the simultaneous London Assembly election. Now Mr Livingstone's personal popularity is apparently much reduced, it should come as little surprise that he apparently faces a desperate battle for survival. In truth, will be a bitter blow for the Tories if Boris Johnson does not become London's next Mayor.

However, in the 36 metropolitan districts outside London, 23 unitary councils (including four new ones), 80 shire districts and 22 Welsh councils where elections are also taking place this year, Labour has little left to lose. True, it would take no more than a small swing for the party to lose Reading, one of only three councils in the south of England outside London that the party still controls.

Merthyr Tydfil, Nuneaton, and Hartlepool are also vulnerable to small shifts in the electoral sands, while Labour could struggle to win control of the new unitary Northumberland council, even though it controls the existing county council.

But at the same time the party will hardly need to make any progress at all to record some gains. Both Jacqui Smith's local council, Redditch, and Jack Straw's backyard, Blackburn, are relatively easy targets, while both Swansea and Sheffield could return to the fold.

If the arithmetic of the elections outside London could be Gordon Brown's salvation, it presents David Cameron with a dilemma. He will be keen to demonstrate his party is advancing. Yet to make significant gains the Tories are probably going to have to do better than they have done at any previous round of local elections since 1997.

A handful of councils in the South could fall into Mr Cameron's lap without too much difficulty, including Thurrock, Gosport, and Maidstone. But his opportunities to demonstrate progress elsewhere are few and far between, Success in the rare chances he does have, especially North Tyneside and the Vale of Glamorgan, will be vital. At the same time the party runs the risk of potentially embarrassing losses in, for example, Rossendale, Walsall and Coventry.

Nick Clegg, meanwhile, faces the misfortune that, in his first year as Liberal Democrat leader, he has to defend one of his party's best ever local election performances

The writer is professor ofpolitics at Strathclyde University