So what does all of this mean? First let's look at the situation for the Conservatives:
- Another Conservative/Liberal Democrats coalition would have 307 combined seats, but would only have the backing of 30% of the electorate.
- Combining with the UK Independence Party (UKIP) might only give the Conservatives 1 more seat, but it adds a sizable chunk of electoral support (rising from 22.4% to 29.6%)
- If the Conservative could combine with the Lib Dems, UKIP, and the Democratic Unionists Party — a party from Northern Island who have often allied with the Conservatives in the past — then they would still only have 316 seats, and this would reflect potential backing of 37.6% of the electorate.
- It's hard to imagine any other party supporting the Conservatives, except for maybe on a vote-by-vote basis.
And for Labour:
- Support from the Scottish National Party (SNP) would add a huge number of seats to a potential coalition (which has already been ruled out), but would hardly change the national backing from the electorate. The SNP only run candidates in Scotland and despite potentially winning almost every Scottish seat, this may only reflect 2.5% of the electorate voting for them.
- In contrast, a Labour/Lib Dems coalition would gain fewer seats than a Labour/SNP deal (293 vs 318) but would end up reflecting much more support from the electorate.
- Labour have more potential coalition partners than the Conservatives, and could possibly form some sort of union with the SNP — yes, I know that I've already said that this has been ruled out but you know…politics — as well as the Lib Dems, the Greens, Plaid Cymru, and the SDLP (the Social Democratic Labour Party of Northern Ireland). If they all joined forces, they could amass 352 seats with backing from 34.7% of the electorate.
Conclusions
So in the unlikely scenario of grand Conservative or Labour coalitions, you still end up with a situation where less than 40% of the electorate would have voted for them. Only if Labour can unite with the SNP, will they have a chance of an absolute majority (>325 seats). The best they can do otherwise might be about 300 seats or so.
I find it interesting that the slice of the electorate who probably won't vote is larger than any single party, and larger than all of the potential coalitions listed above bar one (the grand Conservative coalition).
Whatever happens on Thursday — and over the following days and weeks — it will probably be true that any resulting coalition is going to be unpopular with most of the electorate.