Leading article: A by-election that obscures as much as it reveals

Norwich North shows that an anti-politics mood is still strong

The furore over MPs expenses might have died away of late, but the Norwich North by-election is evidence that the affair continues to cast a shadow over Westminster. One of the ironies of yesterday's result is that it suggests the Government shot itself in the foot with its panicked reaction to the expenses firestorm.

Visitors to East Anglia in recent weeks discovered a healthy number of constituents who spoke of their support for their former Labour MP, Ian Gibson. Rather than baying for Mr Gibson's blood over his supposed expenses abuses, they felt he had been harshly treated by Labour's disciplinary "Star Chamber". If the party had been less severe, Mr Gibson would not have resigned, postponing this contest until the next general election. As it was, Labour got the worst of both worlds: an early poll and the alienation of many traditional Labour voters.

Of the other main parties, the Liberal Democrats will also have been disappointed by the result. The third party has been performing impressively on the national stage of late. Nick Clegg has set the political agenda on issues such as the British residency for Gurkhas and he has been admirably upfront about the economic choices facing the country. But the Liberal Democrats seem to have mislaid their talent for turning national exposure into by-election victories, trailing a weak third in Norwich North.

The Tories were understandably pleased yesterday with the comfortable election of their young candidate, Chloe Smith. They were able to point to the 16.5 per cent swing from Labour as putting them on course for an overall majority at the next general election.

Yet a close inspection of yesterday's results does not suggest a Conservative Party comfortably cruising to power in the manner of the Labour Party in 1997. The Tories certainly produced a decent swing, but they increased their share of the vote by less than they did in last year's by-election in Crewe and Nantwich. There were no mass defections of Labour votes to the Tories. That will concern Mr Cameron and his team.

Part of the explanation is that smaller parties did impressively in Norwich North, just as they did in last month's European elections. There was a sense of disappointment in the Green Party camp yesterday, with some feeling they ought to have done better as a strong opposition force on the local council. But they still doubled their vote on 2005. And UKIP also did formidably well. The anti-government mood in the country is vying for predominance with a mood of antipathy towards all the mainstream parties.

The Conservatives will regard Norwich as a springboard, and Labour will live with the result. It seems unlikely to prompt fresh rebellion against Gordon Brown. The party's rebels are still demoralised by the last failed coup and, with Labour MPs scattered around the country in the parliamentary recess, it seems fanciful to imagine another plot materialising over the summer.

So, in one sense, Norwich North obscures just as much as it reveals of the political landscape. If the anti-government feeling grows stronger in the country between now and next spring, the Conservative momentum will, surely, become unstoppable.

But if, instead, the generalised anti-politics mood increases, then so does the uncertainty over what the next parliament will look like. As they while away their long break, one thing MPs cannot complain of is lacking food for thought.