Why, on the eve of Eastleigh, the allegations relating to Lord Rennard reach right up to Nick Clegg's door

This scandal could hardly come at a worse time for an already bruised party

Lord Rennard, former Lib Dem chief executive (PA)

The Liberal Democrats were just beginning to believe they had turned a corner after losing millions of supporters since the formation of the Coalition.

For once they had some good news as private polling in the pivotal Eastleigh by-election showed the party was heading for victory over Conservative challengers.

To their relief, they discovered that the cause of the by-election – former Lib Dem minister Chris Huhne’s dramatic resignation after admitting lying over a driving offence – was not harming them much on the doorstep.

Nick Clegg even felt confident enough to fly off for a brief family holiday at his in-laws’ home in Spain.

He touched back down in Britain last night to discover his party engulfed in yet another crisis – and this time one that reaches all the way to his own office.

For days his aides denied he knew anything of the rumours that had swirled around Chris Rennard three years ago – despite the fact that they were common knowledge in the Westminster gossip-factory and had been hinted at online. Lord Rennard has denied all the allegations levelled at him.

The denial of any knowledge was repeated yesterday by Vince Cable, the Business Secretary, and Jeremy Browne, the Home Office Minister.

As the party changed its story last night, Mr Clegg sought to differentiate between being aware of “concerns” about Lord Rennard’s alleged conduct and the specific complaints of sexual harassment first raised last week by Channel 4 News.

It is a very fine distinction to draw, leaving the Deputy Prime Minister struggling to contain dangerous and deepening turmoil. Its implications will reverberate well beyond Eastleigh.