The recent era of majoritarian rule in the UK is drawing to a definitive close. On 7 May, for the first time since 1910, voters will almost certainly return a second successive hung parliament. In the absence of a 1992-style polling debacle (when the Conservatives finished 7 points ahead of Labour on election day, having been tied in the final surveys) or an extremely late swing, both of the main parties will fall far short of the 326 seats required for a majority.

The memory of two triple election-winners, Margaret Thatcher and Tony Blair, has made single-party hegemony appear the norm. But in previous decades, the reverse was the case. Of the 20 governments formed in the 20th century, half were coalitions or minority administrations (with five of each). We are almost never in “uncharted territory”. David Cameron recently warned of the SNP: “This would be the first time in our history that a group of nationalists from one part of our country would be involved in altering the direction of the government of our country.” One can only assume that, as in the case of his preferred football team, the Prime Minister suffered a “brain fade”. Between 1885 and 1914, Irish nationalists campaigning for home rule played precisely the role he described.

In 2010, the solution to the UK’s first hung parliament since February 1974 was quickly devised through a coalition between the Conservatives and the Liberal Democrats. The parliamentary arithmetic made it the inevitable administration (Labour and the Lib Dems combined were still 11 seats short of a majority). With a haste rare in Europe, where governments are typically formed over weeks, not days, it entered office with a comfortable majority of 78 seats. It survived for a full parliamentary term and proved more stable than some of its single-party predecessors. No one in Westminster expects the coming days, or the coming years, to be this smooth.

None of the main election forecasts suggests that Labour or the Tories will win enough seats to govern with the Lib Dems alone. The manifesto of Nick Clegg’s party was crafted with the aim of returning to office in mind. It avoided making policy pledges that would be obviously unacceptable to either side. A £12,500 income tax threshold, £8bn more for the NHS and ring-fenced education funding are among the uncontroversial demands that appear on its front cover. The Lib Dems have also avoided explicitly rejecting either Labour’s or the Tories’ most cherished policies (including the latter’s EU referendum pledge). But the numbers will likely preclude a bipartisan deal. For a majority, Labour and the Tories will need to look elsewhere: to the SNP, the Northern Irish DUP and, in extremis, Ukip.

It is this foreboding arithmetic that explains why Britain is increasingly likely to be led by a minority government after the election. To their principled objections to another coalition, Tory backbenchers can now add a pragmatic one: it wouldn’t give them the numbers anyway. Most of Labour’s shadow cabinet have long believed minority government is preferable if the party falls short of a majority. It is also the option privately favoured by Ed Miliband. The Labour leader regards the broken promises and diluted policies of the past five years as proof that coalition is an unsatisfactory form. Far better for a party to put its programme before the House of Commons and let it stand or fall. Whether victorious or defeated, the toxic charge of “betrayal” is averted. The Labour leader is emboldened by the belief that few will want to vote against policies as popular as a higher minimum wage or increased housebuilding.

Added to this attraction is the monopolisation of ministerial posts by members of the largest party. “Could you imagine David Laws working as chief secretary [to the Treasury] alongside Ed Balls?” asks one Labour adviser. Many in Labour remain culturally averse to sharing power, not least with the “treacherous” Lib Dems. Clegg’s vow not to form a coalition with Miliband that is reliant on “life support” from the SNP has only lengthened the list of obstacles.

If most of the current projections are correct and Miliband is the only leader capable of assembling the 323 votes required for a de facto majority (absent the Speaker and the five abstentionist Sinn Fein MPs), the UK could have its first minority government since James Callaghan fell in March 1979 (excluding the final months of the Major administration). Labour has ruled out both a coalition with the SNP and a confidence-and-supply arrangement. Miliband would become prime minister even if his party finished second on votes and seats (as in the case of the first Labour prime minister, Ramsay MacDonald, in 1924). Rather than whether such a government would be “legitimate” (it would by definition), the more pertinent question is if it would work.

Minority governments are historically regarded in Britain as solitary, poor, nasty, brutish and short; daily horror shows in which terminally ill MPs are liable to be wheeled in to the Commons to vote on some critical agricultural motion. MacDonald’s administration lasted just nine months before it was brought down by the Conservatives and the Liberals over the suspended prosecution of the Workers’ Weekly for “incitement to mutiny”. But minority governments can endure and even succeed. Whether they do is largely dependent on political circumstances.

The SNP minority administration that ran Holyrood from 2007-2011 survived for a full term because it was not in the interests of its opponents to bring it down. There was no incentive to hasten a second election at which the Nationalists were (correctly) expected to thrive. With the aid of the Tories (a fact that neither party is keen to draw attention to), the SNP was able to pass successive budgets and keep 84 of its 94 manifesto pledges.

Having led one minority government at Holyrood, the Nationalists’ contention is that they can now control another at Westminster. Nicola Sturgeon recently pledged SNP support for a Labour Queen’s Speech but argued that “how you exercise influence on an issue-by-issue, vote-by-vote basis” is more important. The Nationalists’ leverage, however, would be weaker than they and the Tories suggest. Their pledge never to prop up a Conservative government automatically restrains their bargaining power. Roy Hattersley, who served in Callaghan’s cabinet, draws a contrast with the Liberals’ position at that time. “The only pressure on the Lib-Lab pact was from the Liberals in the country. The Liberals in the country didn’t want them to prop up a Labour government,” he told me. “The Scottish National voters desperately want a Labour government. Therefore the pressure is on them to come to a compromise with Labour in a way it wasn’t under David Steel. The trump card that Ed Miliband has in his hands is that Nicola Sturgeon will never be forgiven by Scotland if she’s instrumental in there being a Tory government.” In March 1979, as Miliband has recently pointed out, the SNP voted with the Conservatives to bring down Callaghan’s administration. The Nationalists were punished at the subsequent election, losing nine of their 11 seats. Thirty-six years later, they would not want to be held responsible for bringing Boris Johnson or Theresa May to power by combining with the Tories to pass a motion of no confidence in Labour (the only means, other than a two-thirds dissolution vote, by which an election can be triggered under the Fixed-Term Parliaments Act).

Minority governments are at their weakest when their opponents unite around a common cause. Yet so minimal is the policy ground between the SNP and the Conservatives that Labour would rarely endure this fate. Because of the Tories’ support for Trident, for instance, there is no threat to renewal – the two main parties will easily outvote the anti-nuclear bloc. The SNP could, in theory, combine with the Conservatives to vote down a budget. But Labour doubts that the Nationalists would dare oppose policies endorsed in their manifesto, such as the repeal of the bedroom tax, the reintroduction of the 50p tax rate, a bankers’ bonus tax and the abolition of non-dom status. The sight of SNP MPs walking through the division lobbies with the Conservatives against such progressive measures would be a gift to Scottish Labour.

Under an alternative scenario, however, Sturgeon’s party could combine with the Labour left to force Miliband to dilute planned austerity. The Labour candidate John McDonnell, the chair of the Socialist Campaign Group, recently told me that he and between 30 and 40 of his colleagues would vote against any budget or spending review that included cuts (and predicted that Miliband would backtrack). In 2009, Alex Salmond faced a crisis when his budget was rejected by the Scottish Parliament – but the week following this defeat, a little-revised package was passed after the SNP leader called his opponents’ bluff by threatening to resign and to trigger a new election (through a no-confidence vote). The Nationalists were sufficiently popular to play this card; a Labour administration may not be.

The inherent disadvantages of minority government should not be understated. Such creatures are condemned to live week by week or day by day, locked in a rolling coalition agreement with the entire legislature. At the mercy of the Commons, Miliband would struggle to be a globe-straddling PM in the mould of Thatcher or Blair – his vote could be needed at any moment. But many of the voices predicting that a Labour minority government would be either fleeting or impotent are the same that forecast an early end to Cameron and Clegg. After the past five years, the UK no longer regards coalitions as inherently unstable. By 2020, it may conclude the same of minority governments.