Leading article: A second-rate contest for a first-rate city

The contest to be the next Mayor of London has begun in true knockabout fashion, with the principal candidates exchanging the sort of Punch and Judy blows that David Cameron said he would eschew in national politics. The duel is between the incumbent Ken Livingstone and his Tory challenger Boris Johnson. Besides these two bombastic characters, the Liberal Democrat Brian Paddick and the Green candidate Sian Berry will have difficulty making themselves heard – which will be the voters' loss, as well as theirs.

The institution of elected mayor has undoubtedly been good for the capital, as for most other cities where it has been introduced. It has given London a voice and a figurehead, although not always, or in every respect, the one voters might have wanted. It has also produced a measure of autonomy and democratic accountability, though in practice not nearly enough of either. In his almost eight years in the post, Mr Livingstone has shown the job's strengths and exposed its weaknesses.

Perhaps his chief merit, however, is to have demonstrated that London benefits from having a mayor – which is why this year's campaign, as it is developing, threatens to be such a disappointment. Entertaining it may be but, if it continues as it has started, it will be conducted as a battle of superficial celebrity and wit rather than substantial policies.

Mr Livingstone has a record to defend, which has pluses (the congestion charge, buses and green measures), and minuses (management of the Tube, little progress on housing and haemorrhages of public money). The victor, whoever it is, will be able to bask in the glory of the 2012 Olympics, which is one reason why the post is suddenly so desirable.

Of course, a close campaign could galvanise voters and increase turnout. But the risk, already all too evident, is that it will degenerate into back-to-back editions of Have I Got News For You. Londoners deserve much better than a match between a self-important controversialist and a clown who uses buffoonery to disguise his undoubted intelligence. They deserve candidates whose stature is commensurate with the dynamic metropolis that is our capital, and a serious and open debate about its future.