Leading article: Mr Clegg learns the pluses – and minuses – of shared power

He held out the hope that by 2015 he might have an even more positive story to tell

What a difference a year makes. The callow, almost embarrassed leader, still smarting from the accusations of tuition-fee treachery, has toughened up and calmed down. With his refrain, "not easy, but right", Nick Clegg yesterday set out to initiate his fellow Liberal Democrats in the exigencies of government at a time of crisis. And for someone sometimes defined by cockiness, he affected humility and spoke of lessons learnt – not just by his party, but by himself. This was how he dealt with the tuition fees debacle.

The leader who rallied his party in Birmingham was a more sombre and more measured character than the neophyte of last autumn, though no less alone. Almost grateful references to "Paddy" (Lord Ashdown), beaming in the hall, testified to a lack of other allies and the need for a political lineage more recent than Gladstone to claim as his own.

Those same acknowledgements also clarified – were clarification needed – how far Mr Clegg leads his party from the right. As the junior partner in a Conservative-led coalition, he was always going to focus his rhetoric on Labour. But his venom, both against the party and its leader, Ed Miliband, leaves the Liberal Democrat leader little room for an about-turn, were Labour to fall short of an overall majority in 2015. This will confirm the suspicions of those Liberal Democrats who felt, and still feel, that their natural partners are on the left. Which does not mean that no coalition with Labour is possible, rather that it will not be Mr Clegg who takes the party into it.

Any leader who agrees to be the junior – in this case, very junior – partner in a coalition must draw a fine line between maintaining loyalty to the government and keeping faith with his party. Yesterday, Mr Clegg chose his distinctions carefully – maybe too carefully. He had a sideswipe at "media moguls" and parties that served vested interests. But the most enthusiastically received section of his speech was his defence of the Human Rights Act which, he said, "is here to stay". If this foreshadows a battle with the Conservatives, it is at least gratifying that it is one in which the Liberal Democrats occupy – indisputably and unconditionally – the moral high ground.

We will find out, when Mr Cameron addresses his conference, whether Mr Clegg's delicacy in other matters reflected a mutual non-aggression pact, or needless deference. As the next election approaches, however – and the start of the campaign will not necessarily be easier to pinpoint in a system of fixed-term parliaments – he will need to hammer home the differences with the Conservatives just as forcefully as he rounded on Labour yesterday.

That task is not impossible. As he rattled off the Liberal Democrat policies brought to fruition – the pupil premium, abolishing ID cards, banking reform, ending child detention, taking the lowest-paid out of income tax – Mr Clegg held out the hope that by 2015 he could have a still more positive story to tell. The challenge will be to tell it in a way that convinces his whole party and the voters, too.

It is not only Nick Clegg who has been changed by government, but his party, at least that section on show this week. The heady expectations raised by the unusual sight of Liberal Democrats taking ministerial portfolios have been scaled back, and a share of government has made the party more professional and more corporate. There is something to regret here: fewer beards, nary a sandal, less character, less rebellion. But Mr Clegg has grown into government, and after 500 days Liberal Democrats have achievements to their name. They must now beware of having won a share of power, only to lose their soul.