The dews are heavier in the garden, the mists gather in the valleys, and there is a morning freshness which tells us the sad news that summer is passing. Even if we were blind to nature's signs, we would know it to be so from the newspapers and commentators. The August silly season stories (my favourite this year was a news item about wireless transmitters being installed on hairy ants from Yorkshire) give way as they always do, to the press's September pre-conference bombardments on the political parties and their leaders.

All party dissidents, minor or not, suddenly find themselves welcome on every front page and in every news studio. Opinion pollsters, out of business during the dead days of summer, suddenly find themselves able to use a late August poll to predict the outcome of an election still three years away. I remember one in 1995, two years from the election in which the Liberal Democrats doubled their seats, which had me losing my seat in Yeovil. Charles Kennedy was told the same in 2001, two years before he led us to our greatest ever score of elected MPs.

Even the normally scrupulous Martin Kettle, writing in Thursday's Guardian, preferred to suggest Armageddon for us in the next election using a mid-holiday poll showing us at 10%, rather than Tuesday's poll in his own newspaper giving us 15%; no comment on the fact that this was precisely in line with our average between 1997 and 2001, before returning 52 seats in parliament. When you have a point to make, any fact will do.

Liberal Democrats have long ago learned to ignore the polls and get on with the job in hand. I should know. I am the only political leader in modern British history who has presided over an opinion poll rating represented by an asterisk - denoting that no detectable support could be found for us anywhere in the land!

We will be judged at the next election by one fact and one fact only. Whether we have had the mettle to stay the course in delivering effective government for our country at a time of crisis. That is the only thing that matters. All the rest is the froth.

History has not dealt the Liberal Democrats the easiest of hands. It does not help that we are trying to prove that coalition government works in such difficult circumstances. Or that those with whom we have to work are not (to say the least) natural bedfellows. These things make life more difficult. But they do not lessen the need to see it through - or the consequences for us if we fail to do so.

We face an existential choice both for our country and our party. Britain is confronting the severest economic crisis for half a century at a time when everyone else is in crisis too. When our major trading partners in Europe are facing economic meltdown. When the traditional foundations of wealth and how we make our way in the world are changing. When conflict and instability seem a growing contagion. And when the whole structure of world power is changing. In these circumstances, who can be surprised that the attractions of easy solutions are more seductive than tough ones, or that popularity is hard to come by.

As it is for our country, so also for our party. When we all overwhelmingly supported Nick Clegg's decision to lead us into government, we knew it would be difficult. We also knew that we were embarked on a course that would change our party as well as our country. Nick challenged us to leave our comfort zone and make the change from a party of perpetual opposition to one capable of carrying the burdens of government.

Without Nick, that decision would never have been made, and the historic opportunity to show who we really are would never have existed. It is the job of our leader to take us into government. I failed; Nick has succeeded.

In my view he has led our party in government, not flawlessly of course, but with a skill no one else in British politics could have matched and a grace under fire that should make us proud. If you want to see how successful he has been, just listen to the complaints from the Tory right.

Of course, now there are plenty of easier courses on offer. In tough times there are always petty ambitions to be aired, the kind suggestions of our enemies to be ignored, and helpful comments from the sidelines to be endured. But there are mighty things to be done in the next year. Getting growth out of hard times; ensuring that even in austerity Britain can remain a fair society; limiting the powers of the state to snoop into our lives; protecting our fundamental rights from attack in the name of security; asserting our independence as we run up to the next election; and preparing the way for the partnerships and policies that will be necessary afterwards.

None of this will be achieved by being distracted by mid-term summer polls, passing newspaper comments, or short-term personal manoeuvring. The right thing for Liberal Democrats to do now is to continue to do what we have done so well so far. Concentrate on the job we set our hands to under Clegg's leadership. Nothing else.

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