Nick Clegg, the Liberal Democrat leader, got one thing right yesterday. Speaking after last night's vote on the amendment calling for a referendum on the EU Reform Treaty (defeated by the government), he described Europe as the issue that had bedevilled British politics for generations.

Quite. He has discovered, to his cost, just how much havoc it can cause. The three-line whip effectively ordered LibDem MPs to abstain in the vote but 15 chose to rebel and vote for a referendum, three of them front-bench spokesmen who have lost their jobs as a consequence. The resignations from Mr Clegg's shadow cabinet team have undermined his authority, less than three months into his leadership. In addition, his judgment has been called into question. This is not where he planned to be when he mapped out a strategy for a tone and a set of policies to mark the LibDems out as distinctive and appealing to the voter. Mr Clegg sought to make his party look principled on Europe but it is the damaging split in his party's ranks, the result of pursuing a risky and deeply flawed tactic, that sticks in the mind.

To stake all on a referendum on staying in or coming out of Europe (the Clegg position) was to miss the boat. The Commons debate on the EU Amendment Bill 2008 was about (or should have been about) whether the treaty by-passed the democratic processes of member states. The government maintained that, as it did not, there was no case for a referendum. The Conservatives insisted that, as the government had promised a referendum on an EU Constitution, it should let the people decide. David Cameron, the Tory leader, is guilty of massaging history as the constitution, which failed at the referendum hurdle in France and the Netherlands in 2005, is different from the treaty.

The government argues, with some force, that national democracy would be preserved under the treaty, which does not amount to a fundamental shift in Westminster's relationship with the EU, and that the Bill was given the fullest possible scrutiny by MPs. On balance, there probably was not a case for a referendum. It is unfortunate, however, that the opportunity to scrutinise the substance of the treaty was lost in the scramble of the parties to attack and stigmatise each other over Europe. Each is divided to one extent or another over Europe and could have been wounded last night.

But it is the LibDems, traditionally the party of Europe, who are, paradoxically, in the biggest difficulty. Mr Clegg is the architect of this situation and he has much to do to restore credibility as well as authority. Taking a rigid line on a soft option tends not to win many friends. Success is not built on a party gaining a reputation for being so principled that it likes to abstain.