Getty Labour’s historic bind If the polls are right, Ed Miliband may be tempted to go for a constitutional overhaul.

There is no more British general election. There is now an English election that the Labour Party has a chance of winning. And a Scottish election, where the Labour Party is set to be annihilated. The result, coming up in poll after poll, points to more than just a parliament with no party in overall control: It points to a possible constitutional crisis.

This is what the numbers say. The Conservatives, the Liberal Democrats, the UK Independence Party (UKIP), and the possible Northern Irish allies of Prime Minister David Cameron — even if he wins the most votes on May 7 as most observers expect — look unlikely to form a majority. But neither it seems will the Labour Party, whether on its own or in bed with the Liberal Democrats, or with any of its micro-allies in Northern Ireland, or the Greens.

If Britain votes this way, the only way Ed Miliband, the Labour leader, can become prime minister is with the support of the Scottish National Party, or SNP. But this party is committed to breaking up Great Britain.

Looking past election day, Miliband may find himself in an almighty bind with two possible options out.

The first is to become prime minister backed by the votes of the Scottish Nationalists and simply try to govern. Miliband has ruled out a formal coalition with the SNP. But he would need their votes in parliament to run the country.

Many Labour politicians dread this scenario. Leftwing Labour MPs would likely be in constant rebellion, supported by the SNP. Every budget, or controversial reform, would risk being voted down. Every day the right-leaning press would accuse Miliband of selling out the English to the Scots. Senior Labour figures fear the SNP, eager to renew the push for another referendum on independence, would wait for its moment to pounce on Miliband for betraying Scotland. This is a government that Labour might soon regret forming.

If Labour does go for it, many in the party fear that such a sorry minority affair could drag on until the Conservatives have a new leader. And the odds are that this would be the uber-charismatic London Mayor Boris Johnson, who is set to enter parliament as an MP in this election. Labour’s concern is that such a weak government ends up being loathed and soon enough chucked out. Labour could lose even more support in its traditional strongholds in the north of England, where UKIP looks set to come second in a large number of seats next month.

Miliband may have a way out of this bind, though: His option two.

Little discussed on the campaign trail is a proposal in Labour’s manifesto to hold a “people-led constitutional convention.” This would be a big step for Britain, which as result of centuries of political evolution, has an “unwritten constitution” where many un-codified customs are treated as laws.

Miliband laid out his plans for one at his party conference last September. Labour’s announcement was broadly ignored by the media, which dismissed it as an idea hatched in a think-tank and of no interest to voters.

As radical as this plan may sound and as little known as it is by the broader public, Labour’s overlooked enthusiasm for constitutional convention is a tempting solution for Miliband.

Here’s how it might work. When the likely news of a hung parliament comes in, the Labour leader could declare that Britain is in a constitutional crisis. He could then invite all parties to join him in a government of national unity, hoping to prompt frontbench Conservative defection with big posts, knowing full well that UKIP and the Conservatives as a party would never join.

Nick Clegg, the leader of the Liberal Democrats, may be open to this idea. He has ruled out any coalition with UKIP or the SNP but left the door open to a government of national unity. Nearly unknown is that Liberal Democrats have also committed in their manifesto to establish “a UK constitutional convention... tasked with producing a full written constitution for the UK, to report within two years.” The party has long lost out in Britain’s first-past-the-post voting system, and both those in the leadership and party activists dream of electoral reform.

If formed, Miliband’s national unity government could immediately host a constitutional convention to write Britain a new federal constitution, and put itself up for re-election in two years time under new rules enshrined in it, which would need to be approved by a referendum.

The ideas thrown around for a constitution include full fiscal autonomy for Scotland, a federal senate replacing the House of Lords, a parliament for England, a proportional electoral system, and a clause written into the constitution that Britain is a member of the European Union. To stop endless votes, the constitution could include a “generation lock,” that only a super majority could trigger more than one constitutional referendum every 20 years.

As a political tactic, a constitutional convention is attractive for Labour: It could win over unusual bedfellows — by stealing their causes — whilst neutralizing them at the same time. The SNP claims it wants full fiscal autonomy, but taking near full control of Scotland’s finances would make Edinburgh responsible for inevitable spending cuts they blame on Westminster. The fall in energy prices is likely to bring steep cuts in Scotland, which depends so heavily on North Sea oil revenues. This could settle the Scottish question for a generation, whilst proving (through full fiscal autonomy) that an SNP Scotland would not become an economic paradise if it left the Union.

Putting the new constitution up for referendum may settle Britain’s tortured European question. Miliband could say to the hard right that the constitution commits Britain to the European Union and that this is their chance to vote on it.

The constitutional option would kill off a growing right-wing campaign to question the legitimacy of a premiership backed by the SNP, especially dangerous if Miliband's party comes second, but only Labour and the Scottish nationalists can command a parliamentary majority.

The constitutional joker card is attractive for another reason: It would likely throw the Conservative leadership off balance, and into internal turmoil, as, leaderless, they would likely clash over the question of European Union membership that has long divided them.

Miliband is known for his cynicism as well as his cunning, and for unforeseen moves in party politics. Those thinking the Labour leader has not thought through his options should remember that he defeated his own brother David Miliband in a race to become Labour party leader with the backing of the trade unions — a move even many insiders did not foresee.

If he becomes prime minister, Miliband could assume that he could dominate a constitutional convention. This is why his manifesto pledges him to hold one. He could use this to achieve at least two big wins that have eluded British leftists for a century: a reformed House of Lords and a reformed electoral system. Labour could also claim credit for having saved the Union. It’s a risky move — yet the alternative is seen within Labour circles as a recipe for misery.

This article was updated on April 27. SNP stands for the Scottish National Party, which was misidentified in an earlier version.