Jonathan Reed: As the leadership fight ends, Labour begins its new battle

Emails and letters have been pouring into in-boxes and pigeon holes pleading for support as Labour's return to opposition means MPs will decide the make-up of the top team rather than the Prime Minister.

It's one of the quirks of Labour in opposition, and why Tony Blair, when Opposition leader, had individuals in his shadow Cabinet who held diametrically-opposing views to his New Labour outlook.

A few of the old guard are making way – Alistair Darling and Jack Straw have already announced they will return to the backbenches – but there is no shortage of candidates wanting to be part of a "new era", the phrase used by Shadow Home Secretary and Hull MP Alan Johnson in his interview in today's Yorkshire Post.

So thick and fast have the pleas for votes been coming that Shadow Defence Secretary Bob Ainsworth, another one standing down, has sent out a message on the internet messaging service Twitter: "I can't cope with it all. I'm now going to move people one place down on my shadow Cabinet preference list every time they ask for my vote."

Most of the existing Cabinet will seek to stand again. Ex-Ministers, who fell out of favour with either Tony Blair or Gordon Brown, or both in some instances, are hoping to make a comeback. And the four defeated leadership candidates will be after eyecatching roles – while also professing loyalty to the victor.

For a new MP like Barnsley East's Michael Dugher, a former aide to Brown, it is an "entertaining" process to watch. But for the new leader – surely David or Ed Miliband – it may just be their first headache following the election.

Hopes of rebuilding the party in their own image will rely on the hand dealt them by their Parliamentary colleagues.

By general consensus, today's result will come at the end of a contest which has dragged on too long. While Andy Burnham and Diane Abbott have struggled to make their voices heard, Ed Balls is widely considered to have been the best campaigner – inflicting embarrassing blows on Education Secretary Michael Gove over the Building Schools for the Future funding fiasco and taking on the coalition over the economy.

He will hope it is at least enough to earn a top shadow Cabinet job. Gordon Brown's former economic adviser, now MP for Morley and Outwood, will not admit that he cherishes the Shadow Chancellorship, but he has repeatedly said that the role should go to the most qualified individual and it was notable he was still issuing press releases on Thursday – once voting had already closed – attacking the coalition Government's deficit reduction plans.

Having made the tough call to challenge his brother, Ed Miliband, the Doncaster North MP, has made sure that his elder sibling David has not been able to have it easy. Union backing for Ed, who has a personal sparkle his brother can lack, has brought in the cash to fund his campaign – but also allowed him to be painted as "Red Ed".

David, meanwhile, has had to put up with the tag of favourite from the start, but has an impressive boast in claiming support across the party from Alistair Darling to Dennis Skinner. Candid Tories would probably admit that Miliband senior would be their least favourite choice, as he is most likely to appeal to the coalition of support that swept Labour into power in 1997.

If fighting the campaign has been arduous, the winner knows the real work starts tomorrow morning – and there are already four urgent tasks requiring attention.

Firstly, nothing is more vital than restoring the party's economic credibility – the crucial ingredient that allowed them to win power 13 years ago.

Voters have accepted the need for spending cuts and tough action on the deficit. As Mr Johnson recognises today, simply opposing every cut – as appeared to happen at times during the leadership contest – is not the solution for a responsible opposition seeking to return to power.

If specific cuts are to be opposed – as they legitimately can and should be at times – Labour should offer an alternative, be it cuts elsewhere or ways of raising extra revenue. Every new spending commitment should be costed and fully funded. And if the pace of deficit reduction is to be challenged, the party must be able to offer a compelling path out of debt rather than pretending it never needs to be dealt with.

Secondly, today's victor needs to fashion an effective machine to hold the Government to account both in the Commons – where coalition Ministers have sometimes benefited from the distractions of the leadership contest – and outside. They should note how, during the Cameron years in opposition, the Tories built up a well-oiled media operation pumping out stories and rebuttals at speed.

Thirdly, the Milibands must unite the thousands of volunteers and activists they each recruited during the contest to create an army of fired-up campaigners who can be a force to be reckoned with.

And finally, Labour could do worse than borrow a little from the Tory experience under David Cameron, when he commissioned policy reviews to generate fresh ideas. Some of the Tory ideas were quickly junked, but others made it into the election manifesto and beyond. Now Labour must use this period in opposition to re-energise – and that must mean a complete policy reappraisal.

A glass of champagne for the victor may be well earned tonight, but there is no time for a hangover tomorrow. It's time to follow the example of the shadow Cabinet contenders, consign the leadership contest to the past – and start looking to the future.

Jonathan Reed is the Yorkshire Post's political editor.