We should not let an extraordinary weekend pass without taking the still somewhat fantastical situation where this weekend's opinion polls were close to the final result, and looking at hypothetical situations of what that might mean.
Let's take LibDems 32, Conservatives 31, Labour 28 as one example. (BPIX/Mail on Sunday). The Mail on Sunday calculation that would lead to LibDems 121 seats, Conservatives 230 and Labour 267 is highly speculative, since the seat predictors (based on universal national swing) tell us very little about how people will vote, in specific constituency contexts, if all three parties were somewhere around 30% with 72 hours to go.
Still, it seems very likely that the electoral system would not cope with a 3-party contest, and would finally be fatally broken beyond repair.
But what would happen in the aftermath if that was the result on May 6th?
In most hung Parliament scenarios, a Conservative minority government is the most likely outcome, and a Labour minority government, or some type of coalition in some others. What is often underestimated is what the public think should happen will have a powerful impact. Those in so-called "smoke-filled rooms" will have the 24 hour news channels and opinion polls very much front of mind.
Firstly, Labour should immediately recognise it would not have the democratic legitimacy to govern alone. Even if the largest party ought to seek a coalition as a matter of democratic legitimacy, with one of the other two parties. (A party with around 30% of the vote and 40% of the seats would surely bear a lot of responsibility in ensuring a government could be formed: if Labour stood entirely aside, a stable government would be difficult without a LibDem-Tory deal). The Labour manifesto offers a good basis for negotiation with the Liberal Democrats - I previewed some possible outcomes when advocating a Lab-Lib coalition back in January 2009: there would be a majority in the House of Commons for the Alternative Vote; but with this type of outcome, public and political pressure to shift towards a more proportional system, such as AV+, might be anticipated.
Secondly, the LibDems as supporters of PR, would be well placed to argue that no party had a mandate to govern alone, and would have a strong claim to shape the course of events. Might Nick Clegg stake a strong moral claim to the Premiership if his party had won most votes, even if third in seats? That case would certainly be strengthened if 75% of the public were saying that he should, and most voters would certainly expect to see his party prominent in government. But a LibDem minority government could not operate with under 150 seats, so this would depend on negotiating with coalition partners on the basis of the manifesto priorities he has set out.
Thirdly, the Conservatives: they are strong supporters of the current electoral system, but would probably not regard such an outcome as a legitimate example of 'rough justice'. (Their reforms do very little to address the causes of such an outcome). Perhaps they should take seriously their argument that the party with most votes should get most seats - and argue that the LibDems ought to govern. A LibDem-Conservative coalition would be one possible legitimate outcome - but the Conservatives might need to at least match Labour's position on electoral and political reform. But having opposed voting reform, the party , might well prefer to stay in opposition and to try to oppose electoral reform in a referendum.
If no agreement proves possible, Labour's role as the current government and largest party might mean a minority government should organise fresh elections. But, with a similar result quite possible, an argument for a referendum on electoral reform prior to the next election would be a strong one.
So it could be that an administration was formed with the short-term focus of holding a referendum on electoral reform and an elected Lords by the summer or Autumn. A longer-term arrangement might be possible, though a coalition could also decide to go back to the country and seek a mandate for a joint programme. All sorts of options would be open - and which prevailed would depend in large part on what chimed with the public mood.
So how to stop this scenario?
The two major parties will continue to seek to win most votes, and an overall Commons majority too. But the Conservatives would be very ill advised to make "Vote Clegg, Get Brown" their primary public argument. Challenged with having displayed a sense of entitlement about inheriting the government of the country, they would do the same thing in spades.
Here are three of the reasons it may not resonate.
1. The Tories may now much overestimate the value of the Cameron/Brown contrast, which appears to be the only argument that they retain confidence in.
On a "forced choice" between a Cameron-led Conservative government and a Brown-led Labour government, the country is now almost equally divided. From YouGov's Saturday tracker:
If you had to choose, which would you prefer to see after the next election, a Conservative government led by David Cameron or a Labour government led by Gordon Brown?
Conservative government led by David Cameron: 44%
Labour government led by Gordon Brown: 42%
Don't know: 14%
If the Tory leader can not do considerably better in the foreign affairs or economy debates, he could yet trail on this question.
2. There is increasing evidence that the "threat of a hung Parliament" argument could yet backfire.
David Cameron is in the odd position of rhetorically inviting the whole country to join his government, while arguing that a House of Commons where parties have to negotiate with each other would prevent firm and decisive government. Does the claim to a new, inclusive politics of spreading power not lose credibility if a core principle is that absolute power is needed to make democracy work?
This is YouGov on a hung Parliament:
A hung parliament with the Liberal Democrats holding the balance of power could be a good thing
Strongly agree: 17%
Tend to agree: 36%
Tend to disagree: 20%
Strongly disagree: 17%
Don't know: 11%
BPIX for the Mail on Sunday found sentiment equally divided between coalitions - Brown/Clegg 27%, Cameron/Clegg 20% - and majority governments, with a large Tory majority (22%), a large Labour majority (8%) and small majorities for the major parties at 8% each.
ComRes had broadly similar findings, interestingly finding that a third of Labour voters would prefer a Labour-led coalition to a Labour majority government, as John Rentoul reports.
Lib Dem voters would prefer either a Lab majority (6%) or Lab led coalition (46%) to an outright Tory majority (4%) or Tory-led coalition (35%). 35% of Lab voters would prefer a Labour led coalition and only 53% a Lab overall majority (compared to 67% of Tory voters wanting an outright win)
3. What David Cameron seemed to lose last Thursday night was his claim to be a "change" candidate. A vociferous right-wing attack on the LibDems risks reinforcing that.
The Conservatives need to climb back towards 40%. One barrier is if they do not counter the LibDem rise; another perhaps equally important is if they sound like the "same old Tories" in their attempts to do so. So there are voices in the party wondering if they should have done more to prepare for a possible hung Parliament: Cameron's sporadic love-bombing of the Liberal Democrats never went beyond rhetorical appeals for them to vote Tory.
David Cameron's party could now spend three weeks running a classic 1980s-style attack to blast the LibDems as dangerous, inexperienced unilateralists who will sell out to Europe. That might then look odd if it looks increasingly like he may want to court them on May 7th.