All sorts of things might change the public mood before polling day, but if nothing does, a Guardian/ICM poll gives a good snapshot of the likely result.

Like most other polls from different companies this year, it puts the Tory lead at about 10 points, the party's share at about 40% and Labour's share at about 30% – the precise scores are 40% to 29%, an increased lead of 11 points. Meanwhile the Liberal Democrats are creeping into contention for an influential third place, at 21%.

Another way of summing things up is to look at the answers to the Guardian's regular "time for a change" question. In the poll 66% think this is a moment for a change of government, against 25% who say continuity matters more and who want to stick with Labour.

These are not far off the figures from March last year. Then 69% wanted change and 25% more of the same. Back in September 2006, when discontent with Tony Blair was at its height, 70% of people wanted change. Immediately after Gordon Brown took over that dropped to 55%.

But now the public mood seems made up. There may be nothing the governing party can do to shift it. Even among people who backed Labour in 2005, 38% think it is time for a change.

Labour's hope must lie partly in the economy, with figures tomorrow expected to show that Britain has finally left recession. But even here the polls have bad news for the party.

Asked whether on balance Brown's leadership has helped Britain through recession or made things worse, 50% say worse – including 28% who say he made things a lot worse. Against that, 43% think he has helped the situation, but only 6% say he made things a lot better, and 37% a little better. If the prime minister is looking for gratitude, he is not going to get it.

Unsurprisingly, Labour voters remain loyal to the former chancellor: 72% think he helped to limit recession. But Lib Dems are unconvinced, and Tory supporters strongly hostile. If recovery strengthens, Labour may not get the credit. Of people who say they voted Labour in 2005, 32% think Brown made the recession worse.

If figures such as these do not change dramatically over the next few months, Labour's main ambition will be to deny the Conservatives a parliamentary majority. This is certainly possible. Last week, at a conference in London, leading pollsters expressed confidence in their methodologies for calculating shares of party support, but there is less certainty about the best way to estimate the number of seats each party will win.

One reason is that this contest will go in at least three directions, with Lib Dem support holding up and the party fighting both Labour (mostly in the north) and the Conservatives (in the south and west). About one in 10 2005 Labour supporters now back the Conservatives, as do about one in five 2005 Lib Dems. Meanwhile One in 10 current Lib Dems has switched from Labour.

Smaller parties however may prove less influential than looked likely during the European elections last year. Put together, other parties are down to 10%, against 15% last June. Nationalist parties in Wales and Scotland account for 4%, the Greens 2%, Ukip 2% and the BNP 1%.