Polly Toynbee has an article in today's Guardian whose headline tells you all you need to know:

Why I can’t forgive Nick Clegg and his party of useful idiots

Those of us who remember Polly Toynbee from the SDP - and even from David Owen's Continuing SDP - find it hard to take her entirely seriously in Tribune-of-the-People mode. We Liberals called them "the Soggies" for a reason.

And there is a dishonesty at the heart of her argument. When she writes:

The Lib Dems swallowed the story that the country needed a boiling down of every function of the state to its bare bones. They were useful idiots for what was always an ideological project

she ignores the fact that Labour fought the 2010 general election promising spending cuts that would be "tougher and deeper" than those implemented by Margaret Thatcher.

In other words, most of the cuts made by the Coalition would have been made by a Labour government too.

But I don't suppose you would make yourself popular with Guardian readers if you reminded them of that.

Even if we can set Toynbee's article to one side, we Liberal Democrats do need to decide the lessons we should learn from the Coalition years. Because I liked seeing us in power and I want to see it again.

So let me suggest three lessons - no doubt there are many others.

First we need to be more politically astute. Even if we are in coalition with another party, its members are not our friends and do not wish to see us prosper.

And I think Nick Clegg now recognises this. As he said in Saturday's major interview with Simon Hattenstone: "I did not cater for the Tories' brazen ruthlessness."

Second, we need a distinct Liberal Democrat approach to economics. One of the problems with the Coalition was that we had four considerable economists - Cable, Huhne, Laws and Webb - on our front bench, yet we ended up with Danny Alexander at the Treasury.

David Laws might have had the intellectual heft to challenge George Osborne (whether he would have wanted to is a separate), but with Danny as chief secretary that was never likely to happen.

We fell too easily into saying that Labour had "overspent on its credit card" - or rather, we said that but had little interesting to add to it.

Third, we need a clearer idea of who the voters we want to appeal to are. The problem with imposing tuition fees was not just that we broke a pledge we should never have signed: it was that we let down the group that should be part of the core vote for a Liberal party: the educated young.

David Howarth's thoughts on this - and the lessons of coalition in general - are worth studying.

One thing I would say in Nick Clegg's defence is that these problems - a certain naivety about power; a lack of economic identity; a failure to decide who we are trying to appeal to - existed in the Liberal Democrats long before he joined.