The Big Question: How do hung parliaments operate, and are we heading for one now?

Why are we asking this now?

For the first time, Nick Clegg has allowed himself to be drawn into speculating which way the Liberal Democrats would jump in the event of a hung parliament in which neither the Tories or Labour gained an overall majority. The Lib Dem leader said it was obvious that "whichever party have the strongest mandate from the British electorate" should have the "first right to seek to try and govern, either on their own or with others".

Clegg's comments make clear he could contemplate entering into an informal pact with David Cameron's Conservatives, who are likely to have the most MPs after the election, but would not consider propping up Gordon Brown in power. Mr Clegg was speaking after an opinion poll suggested that Labour had narrowed the gap on the Tories to six points, setting the scene for a hung parliament.

What are the chances of that?

It's far too early to put any money on it. The likelihood is that the Ipsos-Mori poll for The Observer at the weekend will prove to be a blip as its findings are out of line with other recent surveys. They show Labour support strengthening slightly since the historic lows of the late spring and early summer, but only by enough to suffer a heavy defeat rather than a rout.

The latest weighted average of the polls for The Independent puts the Tories on 42 per cent, Labour on 28 per cent and the Lib Dems on 18 per cent. These figures – producing a Tory majority of 90 – would mean there is no need for Mr Cameron to start mugging up on Lib Dem policy just yet. Andrew Hawkins, of pollsters ComRes, says he believes there is a 30 to 40 per cent chance of a hung parliament if Labour continues to put pressure on the Tories.

What would happen if there was a hung parliament?

Suppose the nation voted in line with the survey and gave the Tories 37 per cent, Labour 31 per cent and the Lib Dems 17 per cent. On a uniform swing (ignoring the local battles in 650 constituencies) that would produce a Parliament with 296 Tories, 278 Labour MPs, 44 Lib Dems, 11 Scottish and Welsh Nationalists, three others and 18 Northern Ireland MPs.

David Cameron would still be 30 seats short of the 326 he needs for the slenderest of majorities and 40 to 45 adrift of a workable majority.

What would happen the morning after the election?

Discreet contacts are already underway between the Queen's private secretary and senior civil servants over how to proceed if the election result proves inconclusive. The last time crown and state seriously debated the issue was in 1992 when John Major and Neil Kinnock were level-pegging in the polls. In 2010 their attitude will be that it has to be left to the politicians, rather than the monarch, to negotiate a stable arrangement that enables government to carry on functioning.

If Mr Cameron had the largest number of seats (which would also mean winning the most votes because of an electoral system weighted to Labour), the onus would be on him to form a government. Would he then seek an informal pact, or go it alone? And has Mr Brown got an "in case of emergency break glass" option – a commitment to electoral reform, perhaps – that could persuade Mr Clegg to eat his words and keep him in Downing Street?

Have we been here before?

There have been several close-fought elections, but the British voters have only once delivered a hung parliament. The February 1974 contest produced a virtual dead heat, with Harold Wilson's Labour opposition winning 301 seats just ahead of the 297 won by Edward Heath's Conservative government. Mr Heath, whose party actually attracted more votes than Labour, tried to strike a deal with Jeremy Thorpe, the leader of 14 Liberal MPs. He failed and Mr Wilson formed a minority government, which soldiered on until October 1974, when he called another election and won a tiny overall majority of three. That majority soon vanished and in 1977 his successor, James Callaghan, negotiated the Lib-Lab pact that kept the government afloat for another year.

So the Lib Dems must be rubbing their hands with glee?

For a generation the third party has been intoxicated by the prospect of sharing power in a hung parliament (although they traditionally preferred the more positive-sounding term "balanced parliament"). It could, some speculate, lead to the party forcing a mould-breaking ballot on changing the voting system as the price of keeping one of the bigger parties in office.

The more sober of their colleagues disagree. As one senior Lib Dem put it yesterday: "It would be a nightmare for us." One example of the pitfalls they would face could crop up in the first 50 days of a Cameron minority administration. By then the new Prime Minister would have produced an austerity budget that causes howls of anguish. Would the Lib Dems support it – seeing cherished social programmes slashed – or vote against the budget? If they took the latter course, that could force another election, with the voters blaming the party for forcing them to the polling booths again.

How would a minority government work?

The proportional voting systems in Scotland and Wales produced hung parliaments in Edinburgh and Cardiff in the last elections (and of course sharing power in Belfast is at the heart of Northern Ireland's political settlement). Each provides a very different example of how that outcome works in practice.

Alex Salmond, whose Scottish Nationalists won just one more seat than Labour in 2007, has operated the ultimate minority administration, challenging other parties to support it on an issue-by-issue basis. He has, for instance, relied on Conservative votes to win approval for his budgets.

In Wales, Labour's Rhodri Morgan, who was much closer to an overall majority, rapidly agreed to share power with Plaid Cymru. It was in the interests of both – Labour regained control of major departments, while Plaid had its first experience of government.

What problems might arise at Westminster?

The first, and biggest, headache for the leader of a minority administration would be to reassure a jittery City. A hung parliament is the result that keeps the money markets, desperate for political stability to underpin a battered financial system, awake at night. The new Prime Minister would have then to reassure other heads of state that he would not be ousted from office in the near future. Finally the prospect of destabilising horse-trading with minor parties – and his own rebellious MPs – and late night Commons votes would loom.

Shadow Business Secretary Kenneth Clarke, who was in Parliament in the Wilson years, claimed last week the prospect of a hung parliament during an "acute national crisis" was worse than a Labour victory. The Tory leader contradicted him days later. After all, it remains possible that Mr Cameron will be wrestling with that very dilemma on the morning of May 7.

Should we worry about the prospect of a government with no overall majority?

Yes

* For a sense of direction and purpose in an administration, an administration needs a good overall majority

Instability in government is the last thing the country needs as it tries to emerge from recession

* Allowing minority parties to wield disproportionate influence over policy is profoundly anti-democratic

No

* All over the world, and within the United Kingdom, there are examples of successful coalition government

* Achieving consensus in government is in the nation's interests in such difficult economic times

* Giving overall power to a Prime Minister on a minority of the popular vote is profoundly anti-democratic