For a leader to make a carefully worded, half-hearted apology is often worse than making no apology at all, and Nick Clegg makes a naïve error if he assumes he can sway a single doubter by saying "sorry" for his pre-election pledge to oppose an increase in student fees. On a crude strategic level his declaration has rebounded on him, giving broadcasters a fresh and legitimate excuse to re-run those excruciatingly embarrassing pre-election broadcasts showing Clegg passionately arguing against any increase, and with dark irony linking his argument with the need to restore trust in politics.

More fundamentally the act of contrition was too clever by half. Students and some other voters are angered by the entire sequence of events – the pre-election pledge and the policy that followed, the tripling of tuition fees. There is little evidence to suggest that they differentiate between parts of the sequence and so they will not be reassured by an apology for the first part but not the second.

Leaving aside the whirl of electoral calculations, Clegg has a case as far as the substance of the policy is concerned. Although a 200 per cent increase in fees was too big a leap in a single move, the methods for repaying the loans were fair and far from punitive. But that is besides the point in terms of the politics of perception and the undeniable breach of trust that the policy has come to represent. Clegg's apology is likely to re-ignite a sense that the Liberal Democrat leader opts for disingenuous public declarations. He genuinely believes that the error was the pre-election pledge and not the policy that followed, but he made the pledge, secured a significant electoral benefit from it, and has to live with the consequences now.

The apology is also mistaken in suggesting that the reversal on fees is the reason for Clegg's bleak personal ratings. It is a symbol of a wider sense of betrayal. Indeed he has stated that the NHS reforms might damage his party more. What is irrefutable is that the polls for the party and its leader are dire and the reasons extend beyond a single policy.

If the economy improves, Clegg could argue that he and his party played a pivotal role in addressing an economic crisis of historic magnitude while ensuring that the Conservatives were constrained on other fronts. That is his only hope of reviving his and his party's fortunes. Limited acts of contrition never work, especially when they are made by a leader so obviously fighting to save both his leadership and his party from electoral meltdown.

Under huge pressure, Tony Blair tried to display a hint of contrition over Iraq in his later speeches and interviews, but he could not really do so because he believed that the war was "the right thing to do", as he put it. The occasional attempts at narrowly defined contrition did not convert or reassure his opponents. Clegg is under similar pressure over his leadership as Blair was then. Like Blair over Iraq, Clegg does not really believe the policy on top-up fees was wrong, so an "apology" looks desperate and calculating, which it partly is.

Even disillusioned voters must accept that Clegg has remained calm in the face of intimidating storms. Yet since his return from the summer break he has shown some signs of insecurity, proposing a wealth tax without any detail and now, with his top-up fees apology, seeking a cathartic moment that risks delivering the opposite of what he intended.

The past has happened and cannot be unmade. Now Clegg needs to stop looking back. He shares in a partnership that his previous supporters have little inclination to forgive, and his apology won't change those feelings. But there are still important, progressive contributions that the Liberal Democrat leader can make to the Coalition.