With the latest opinion poll showing a significant narrowing of the gap between Tories and Labour, down to 6%, which would result in a hung parliament, there is only one question worth asking your Lib Dem candidate in a parliamentary seat where the party stands a chance of winning. (So that rules out Bristol West then....)
That question being: if the latest poll turns out to be accurate and the two main parties come within a couple of seats of each other, which party would you support to form a government? Because let's face it, whether you're voting Lib Dem to keep the Labour candidate out or Lib Dem to keep the Tory candidate out, you need to know whether your vote for the 'Not Labour' candidate or the 'Not Tory' candidate is actually a vote for someone who is then going to betray you by backing a Labour/ Tory Government (delete as applicable).
I will concede, reluctantly, that such a thing as a 'proper' Lib Dem voter may actually exist. (In small numbers. And in strange places. Where people don't know any better.) But even if you've voted Lib Dem on principle (Why?) then I assume you'd still want to know which side of the fence they'd jump off, were they to be forced into a position where they had to do so.
In the past the Lib Dems have had academic arguments amongst themselves as to whether they should support the party with the highest number of seats, or, being true proportionalists, the party with the highest percentage of the vote. I have suggested, kindly, that they should instead base their decision on principle and look to support the party which most closely reflects their political values, but this have never provoked much of a response. Nick Clegg has today, however, as good as announced that he would back the Tories if they got marginally more votes than Labour in the 2010 General Election, which I suspect will go down rather badly with those of his troops who see the Lib Dems as part of the progressive wing of British politics. And with those Lib Dems who are attracted by the Labour promise of a referendum on AV, as compared to the blanket hostility to any form of electoral reform from the Tories.
Clegg's dilemma at this stage is obvious. Some of their seats are Labour/ Lib Dem marginals; some (the majority) are Tory/ Lib Dem marginals. Incidentally, I think this explains why Nick Clegg is only tentatively kicking around the ball marked 'Afghanistan'. He knows that the Lib Dems lack the USP they had in the 2005 election, of being anti-Iraq and anti-tuition fees (though they're still trying, rather limply, to fly the flag on the fees issue). He knows that to oppose our engagement in Afghanistan would win the Lib Dems votes in some quarters, probably from the left, but he's not sure whether it would also lose them votes in their southern heartlands, so he can't quite go there.
But his balancing act is not just limited to Afghanistan. He has to maintain this stance of being Not Labour for voters who don't want to vote Labour, and Not Tory for voters who don't want to vote Tory, but also Labour-lite for people in LibDem/Tory marginals who hate the Tories and Tory-lite for people in Lab/LibDem marginals who hate Labour, but also Labour-lite and/or Left-of-Labour in Lab/LibDem marginals where people hate the Tories but are for one reason or another fed up with Labour.
Perhaps this is why, instead of being able to discuss the coalition issue in terms of broad principle and what sort of policy platform he'd want to support, he has to reduce it to a mere numbers game? Because, as a supporter of proportional representation, he can't really believe that a party which gets, say 37% of the vote compared to another party getting 31% and 'others' picking up the rest, has an indisputable right to rule, regardless of what their policies are and the degree of support they'd attract from the 63% who didn't vote for them. Can he?
The other possible interpretations of this are that (a) Nick Clegg thinks the Tories are going to win and is getting cosy with them now in the hope of a decent job in a Tory Cabinet or (b) Nick Clegg is really a Tory at heart, who's just a bit keener on Europe than the rest of them. And it's easier to imagine Clegg in a Cameron government than imagining him entering the Labour fold (he told me once he thought Labour was far too tribal - too damn right we are!) But whether his troops will follow where he wishes to lead... that's another matter entirely.
Anyway, it's entirely hypothetical. 6% behind, all to play for - game on!