Leading article: A new leader must create space for the third party

It felt like nothing so much as the morning after the night before. There was no rush of hats thrown into the ring, and precious little public gossip about the succession. Likely candidates said they needed more time to decide; Sir Menzies' resignation had come with so little warning.

But a certain fractiousness was already apparent. Lord Ashdown tried to pour oil on troubled waters by describing Sir Menzies' departure as "a selfless act by an honourable man who put his party first". Before the day was out, however, he was contradicted by the man himself. In a BBC interview, Sir Menzies admitted to feeling "irritated and frustrated". He was irritated, he said, by the trivia that surrounded his leadership, and frustrated at not having the opportunity to lead the party into a general election where "our policies and our principles and our values would have been right at the very centre of the political agenda".

While illustrating graphically why he might not have been well-equipped for the cut and thrust of today's politics, Sir Menzies spoke more truly than perhaps he knew about the difficulties facing his party. In the long run-up to the next election, it is quite likely that the policies and principles of the Liberal Democrats will indeed be at the centre of the political agenda. Unfortunately – so far as their distinctive appeal is concerned – this is precisely where the other two parties also aim to be. The third party will be squeezed as rarely before.

This should not mean, however, that the Liberal Democrats are doomed. It means rather that their new leader, whoever it is, will have to marshal all the considerable ingenuity the party has shown in the past to come up with new ideas consistent with the party's traditions and principles.

The Liberal Democrats pioneered "green" issues. No one can take this aspect of forward-thinking away from them. The other two parties have had to run to catch up, but there is no reason why the third party should not forge out ahead again. Their proposal for a tax on flights, rather than passengers, may have been stolen twice over, but it has not been implemented. Alternative sources of energy and the use of the tax system to foster environmental responsibility could still be assets for the Liberal Democrats.

The Prime Minister gives every indication of wanting to withdraw all British troops from Iraq before the next election. But the Liberal Democrats can – and should – trade on their difference: that they alone had the foresight and moral courage to oppose that ill-conceived war. They perpetuate that difference in their approach to civil liberties and migration. Without this third party, the centre of British politics would not be where it is.

Perhaps the greatest strength of the Liberal Democrats is their popularity at the grass roots. In elections their support has invariably exceeded poll predictions, even though the first-past-the-post system works to their disadvantage. The same sense of localism may explain why successive leadership crises have left the party's election results relatively unscathed. The question now is how many more votes the Liberal Democrats might be able to garner with a forceful and innovative leader, and one who knows how to use the many tools of the modern media to best advantage.

At this stage, the lack of a ready-made national star to inherit the leadership is no liability. Few had heard of David Cameron before his spell-binding conference speech two years ago. The new Liberal Democrat leader has the best part of two years to make a mark. The task will not be easy, but the last two messy departures do not automatically make it mission impossible.