The timing of the Liberal Democrats’ spring conference in Brighton is benevolent and calamitous in equal measure

After last week’s Eastleigh by-election victory, the party has much cause for celebration. But the debacle over Chris Huhne and Vicky Pryce – now awaiting sentencing – and the allegations still whirling around the misconduct of Lord Rennard, the party’s former chief executive, cannot but cast a pall over proceedings. As the consequences of both scandals extend to apparently explosive questions of who knew what, and when, senior figures will struggle to escape such questions over the coming days.

The ambiguous atmosphere is reflected in the conflicting public statements from those high up the hierarchy. In a surprisingly naive interview, the party’s president, Tim Farron, described Liberal Democrats as having the qualities both of “nutters” and of “cockroaches after a nuclear war”. Never mind that Mr Farron was trying to characterise his activists’ admirable resilience; he did so in a way that is a gift to their opponents. In contrast, Sir Menzies Campbell, a more experienced former party leader, is upbeat, talking of optimism without complacency. And at last night’s pre-conference rally, Nick Clegg was jubilant over Eastleigh and called on his party not to be disheartened by those predicting electoral disaster ahead.

That was just the beginning, though. Mr Clegg’s task this weekend, and in the months ahead, will be defined by his party’s wildly conflicting mood music. Above all, he needs to make unmistakably clear what matters and what does not, regardless of the headlines.

Questions about who knew what in relation to Mr Huhne and Lord Rennard will soon subside – not least because senior figures can argue, with some justification, that if they responded to rumours in politics, then they would do little else. After all, until the start of his trial, Mr Huhne denied he had asked his then-wife to take the rap for his traffic offence; and Lord Rennard still denies allegations of sexual harassment. Both issues raise questions about the culture of a party not used to scrutiny. But the waves are small in the context of the increasingly fractious political climate within both the party and the Coalition.

Of far greater significance than either Mr Huhne or Lord Rennard are Vince Cable’s veiled calls, in a magazine article earlier this week, for increases in capital investment. Even more so against a backdrop of growing Liberal Democrat resistance to the Chancellor’s calls for further cuts in other areas, particularly welfare. The contrast with attitudes within the party during the 2010 spending negotiations is striking. Then, Liberal Democrats were largely united in support for the austerity programme and the two ruling parties worked together. Now, however, the differences are more marked.

A growing divide is inevitable, given the fragility of the economy, the political hit that the Liberal Democrats have suffered in coalition, and the approach of the 2015 general election. But the party is also increasingly internally split. Although Mr Cable has claimed that his analysis weighing up the pros and cons of extra, debt-funded infrastructure spending is no departure from the Coalition’s economic orthodoxy, the Business Secretary’s allies in the party have tabled an emergency motion urging “radical action to get growth going”. Mr Clegg, however, rejects the proposal out of hand.

Faced with such restiveness, Mr Clegg must reassure his party this weekend that more will be done to boost growth, without making it impossible to reach agreement with David Cameron and George Osborne. The task is a difficult one, marking the start of the hardest phase yet on his tempestuous political journey. It is, though, the only route he can take.