John Curtice: None of the pretenders can offer salvation

We should not be surprised that another attempt is being made to put Gordon Brown's leadership to the test. Labour still seems headed for defeat when the country goes to the polls. If the Prime Minister is to be unseated before the election, the issue can hardly be delayed much longer.

True, Labour's position looks a little better now than it did last June, when the resignation of James Purnell gave rise to major doubts about Mr Brown's future. Then our regular monthly poll of polls put Labour on just 24 per cent. Now it stands on 29 per cent.

Trouble is, the Tory vote has consolidated too. In June both major parties were suffering from the advance of smaller parties in the wake of the MPs' expenses scandal and the Euro-elections. The Tories are now back on 40 per cent, three points up on June.

Consequently David Cameron still has an 11-point lead, enough for an overall majority of 20. Labour would be left with 239 seats, just two-thirds of its current tally. The party would be back to the dark days of the 1980s.

Meanwhile, Labour's position is far worse now than it was 12 months ago. Then the party had reduced the Tory lead to just five points. It apparently had a realistic chance of at least still being the largest party after the election. That possibility now seems extremely remote.

So what can Labour MPs do? The Prime Minister is certainly deeply unpopular. All the polls agree that fewer than three in 10 voters are happy with the way he is doing his job; as many as two-thirds are unhappy.

Indeed, Mr Brown is at least as unpopular now as Mr Major was at this stage before the 1997 election – shortly before he led the Tories to catastrophic defeat. Mr Brown's current satisfaction rating of 28 per cent in the latest MORI poll is slightly less than the 30 per cent John Major scored in December 1996. Similarly his latest YouGov rating of just 23 per cent is a little short of Mr Major's equivalent reading of 25 per cent.

But would Labour MPs be sensible to ditch Mr Brown? They have to ask themselves three questions.

First, how far is Mr Brown's unpopularity simply a reflection of the unpopularity of the government he leads? Changing the man at the top may not be sufficient to persuade voters to forgive and forget.

Second, is there anyone who could do a better job of presenting the party's case? Doubts have been expressed about whether either of the two leading contenders to replace Mr Brown, Alan Johnson and David Miliband, really could touch a popular chord with the electorate. Both are certainly still largely unknowns to many voters.

Third, can Mr Brown be deposed without inflicting terminal damage on the party's electoral chances? To avoid that any move against Mr Brown needs to be swift and united. Such a development is still awaited.

John Curtice is professor of politics at Strathclyde University