After Thursday's result many have suggested a need for reflection on Labour's fundamental values, either before or in parallel with the leadership election.
That is, of course, necessary after such a disappointing result.
This reflection must not, however, come at the cost of leaving a political vacuum to the right. We must resist the urge to navel gaze for too long, given that we are possibly (and some say likely) less than twelve months away from a referendum on membership of the European Union.
The beginnings of a cross-party 'in' campaign are already in place, with Lord Mandelson as the key Labour representative. But the Scottish referendum clearly demonstrated the negative consequences of Labour being identified with an 'elite', 'establishment' consensus.
There are three reasons why a Labour (rather than cross-party) 'in' campaign could -- and I hope, will -- offer the first step towards rebuilding Labour.
First, despite the disappointing result, more people were engaged in political activity this election than ever before -- the vast majority of them, with the Labour Party. No less than 200,000 people left their comfort zone to tap on doors and speak to complete strangers as Labour canvassers.
For many I spoke to, from Milton Keynes to Dover, this was their first experience of political activism. Labour as a party must ensure it is not their last engagement in organised politics. This can be done by offering people a meaningful role in an optimistic, forward-looking 'in' campaign.
Second, many of those new, often young (in age or spirit) activists were energised by the very values that Labour is trying to pursue in Europe. They abhor the xenophobia of UKIP and reject racism instinctively. They care passionately about increasing living standards, not just for themselves but across the world. They are disturbed by current rates of youth unemployment, and would be appalled by the job losses that would occur if Britain cuts itself off from the rest of Europe.
They are also often passionate about the need to tackle climate change and air pollution, viewing these issues as core to Labour's progressive message.
A strong Labour 'in' campaign offers a chance to champion these values. It also gives Labour a chance to offer hope to young people, capitalising on the wave of support from younger people that arose in the latter stages of the election campaign (even if that did not always translate into votes, given the challenge we still face in getting younger voters to turn out in the same numbers as their parents and grandparents).
Labour should now repay that commitment by demanding that 16-year-olds be given a vote in this referendum, and redouble its efforts to register young voters, more necessary than ever before given the Tories' new, US-style measures to make registration harder.
And third, a progressive 'in' campaign offers an excellent chance for local Labour parties to renew their links with trade union members. Just as it was the trade unions who made much of the running against UKIP over the last two years, so it has been the trade unions who have loudly and proudly argued for Britain's continued place in Europe.
A strong Labour campaign, joint with trade unions, will not only be essential to mobilise 'in' voters, but also important in ensuring that Cameron's 'renegotiation' does not remove the working protections and social rights that stop Europe from being just a trade club for multinational companies. It will also prevent accusations that the 'in' campaign is dominated by captains of industry and not representative of working people, a card that UKIP has attempted to play in recent months.
Labour activists, politicians and supporters will need some time to lick their wounds and regroup. But as soon as this is done, we must move quickly to mobilise again all those people who put worked so hard for a better, fairer future for Britain, and provide hope to all those who, despite all the smears and brickbats, did opt to vote Labour last Thursday.
Despite the spin, we know that there is a large body of support across the whole of Britain, and particularly amongst the young, for membership of an EU focused on jobs and living standards. Labour cannot waste any time in arguing for it.