Leading article: A good week for Gordon Brown, but a hard lesson for David Cameron

Two unrelated developments have altered the political landscape. The decision by the Crown Prosecution Service not to press charges in the cash-for-honours question raises several important issues about the way the police went about the investigation and how we fund democratic politics. It was also a highly charged human drama, which dominated the final months of the Blair era. Yet it is almost certainly the outcome of the two parliamentary by-elections in Ealing and Sedgefield that will make more waves over the summer.

The Conservatives came third in both. These would be bad results for the main opposition party in any parliamentary midterm. But they raise awkward questions for David Cameron. He visited the Ealing Southall by-election six times, an unprecedented level of engagement for a leader of the Opposition. On the ballot paper the Conservative Party was presented as "David Cameron's Conservative Party", a form of personal branding that is rare in a by-election. Mr Cameron also approved a candidate who it later emerged had been a recent donor to the Labour Party, a casual approach to campaigning that was predictably and ruthlessly exposed.

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The poor result shows that the Tory leader cannot rely on personal appeal and that his strategy needs readjusting. He has sought to follow the tactics of New Labour when in opposition, but at the equivalent stage of that Parliament New Labour was winning by-elections by large margins, not finishing third.

Since becoming leader, Mr Cameron has broadly pursued a sensible strategy of moving towards the centre ground. But at times he has appeared to be acting opportunistically and superficially. Evidently his party's policy review will be a pivotal moment in his leadership, giving some substance to what has become a less than convincing image. Making policies that have a broad appeal and yet satisfy the activists is never easy. The poor showing in the by-elections will make the task more challenging still.

Labour and the Liberal Democrats have cause for modest celebration. If Labour had lost one of the by-elections the Brown honeymoon would have come to an abrupt end. Instead, in a midterm they won both, confirming rather than jeopardising the Brown Bounce.

In advance of these results there had been renewed speculation about the future of the Liberal Democrats' leader, Sir Menzies Campbell. The respectable performances means Sir Menzies can relax at least for now. His party came second in both. His summer will be less torrid than it would have been if the Liberal Democrats had trailed in third place in Ealing.

While the by-elections have changed the shape of politics, at least over the summer, the collapse of the cash-for-honours inquiry raises broader questions. Yesterday the Crown Prosecution Service outlined the amount of firm evidence that would have been required to bring charges. The criteria were so detailed that we wonder why the police ever thought they had the chance of successful prosecutions in the first place. Assistant Commissioner John Yates said that he took the allegations with the utmost seriousness but that does not explainwhy the inquiry took so long and cost so much. The issues at stake were undoubtedly serious. The secrecy behind the funding of parties and the inducements offered to major donors lie at the heart of the debate about democratic trust. But whether the criminal law rather than parliamentary scrutiny was the right way to tackle the issue must now be open to question.

But these issues are not new and have been whirling around since the start of the long police inquiry. With good cause party leaders will spend more time looking at the fresher lessons to be learnt from the by-elections.