In supporting George Osborne’s ‘fiscal contract’, Nick Clegg mapped out his party’s future – and his own

The Lib Dem leader has reduced the chance of a coalition with Labour in 2015

Charles Kennedy once declared that his party had grown up and was “wearing long trousers”. He was a little premature, but it is certainly the case now that some of the Liberal Democrats’ old oppositionist tactics – ones that used to infuriate their bigger rivals – have gone. Their hand forced by the vagaries of the electoral system, the party found itself in a Coalition with its enemies. After a turbulent start, they have matured in office.

Now Nick Clegg has added another wisp of grey at the temple to his party’s economic policy. In signing up for George Osborne’s “fiscal contract” and a further period of restraint on public spending, he is certainly not going around trying to buy votes. Unlike at the last election, his party will not go into 2015 promising more than they can deliver. This is politically hazardous. Ask any Liberal Democrat what makes their party different and they will tell you it is that it is “democratic”. Thus far, with much grumbling, members have gone along with most of Mr Clegg’s ideas. In return, he has taken them to places no Liberal Democrat has ventured before. This may be more than their consciences – and their political interest – can bear.

Is Mr Clegg in effect ruling out a deal with Labour in the next parliament, even though that may be the only combination that can deliver stable government if neither of the main parties gains an overall majority? He isn’t; but he is making it harder. If Labour is much the largest party, and invites the Liberal Democrats to discuss an economic plan for the next five years, Mr Clegg may have to waive his agreement with Mr Osborne.

Despite the grumbles we report today, events of the past few months have strengthened Mr Clegg. After a good party conference, he has rarely had more authority as leader. If he were replaced, for instance by Vince Cable or Tim Farron, they would inherit policies that they may have opposed privately, or indeed publicly, not so long ago – assuming they stick with the Tories. If it is a Lib-Lab administration it would be even worse; a new Liberal Democrat leader would have to renounce the central planks of economic policy proposed only weeks earlier at a general election. This is Cleggonomics: by tying his party to the Coalition’s economic agenda, Mr Clegg has tied his party to him.

It is almost as if – perish the thought – Mr Clegg were manoeuvring his party and pre-empting its next manifesto before anyone else has a chance to get near to it. Next May’s European elections, in which Lib Dems could come fifth, will be extremely difficult for him, but he will survive.

Committing the Lib Dems to a continuation of Coalition strategy puts his party in an unfamiliar position: promising less than it could deliver if it gave itself a freer hand to negotiate with Mr Cameron and Mr Miliband. But it is the mark of a serious party; and, moreover, it is the mark of a party of government .