As I've said before, I'm generally a Labour voter, but my support is not of the unconditional, 'my party right or wrong' variety. The fact that the floating of
this proposal a couple of weeks ago got me thinking about this probably tells you what I think of it (
Tim Worstall puts it better than I could), but I did reach some conclusions on the general issue. So, here are my top 6 [hypothetical] reasons for voting Tory (or anyone else non-Labour):
1. Policy DisagreementFirst up, it's always possible that the Labour Party could come up with a manifesto that I wouldn't vote for. This could be a matter of general positioning - a situation where they moved sufficiently far along the political spectrum that they were no longer the party closest to my own views - or conceivably could be the result of one 'deal-breaker' policy.
2. Chronic IncompetenceSpeaks for itself really - however close the manifesto is to my preference for how the country should be governed, if they can't deliver then the outcome won't be close, which is what matters. It would be preferable to have an imperfect programme, perfectly delivered, as opposed to a perfect programme that never leaves the drawing board.
3. Tactical VotingI subscribe to the view that we are responsible for the unintended but foreseeable consequences of our actions, as well as the intended ones. Therefore, if my constituency was likely to be contested primarily between the Tories and the BNP I would consider it morally reckless to vote Labour and risk a BNP victory. To pose a more likely scenario, in an election the Tories were expected to win I would vote Lib Dem in a Lib Dem / Tory marginal on the basis that reducing the Tory majority would tend to drag them towards the centre.
4. Bad Local CandidateAnother one with a couple of sub-clauses. Firstly, if I was in general agreement with the Labour manifesto, I would be disinclined to vote for a persistent critic of the Labour leadership. One high-profile far-left nutter (I'm sure you can think of some examples for yourself) does more damage to the electoral chances of the Labour Party than one anonymous Tory backbencher, and probably doesn't vote with them any more often either. Alternatively, a candidate who was politically sensible but personally corrupt would lose my vote equally reliably.
5. It's a good one to loseSometimes losing an election is good for you in the long run. Although it didn't feel like it at the time, 1992 was one of these for Labour. Black Wednesday, followed by several years of scandal and infighting, did such damage to the Tories' reputation that they were condemned to a decade out of power. If Labour had won in 1992 Black Wednesday would have happened to them just the same (ERM membership had cross-party support), it would have seemed to confirm the claim that Labour could never be trusted with the economy, and they could have lost in 1997. This raises the question that, if you're sure that an election is a good one to lose for your party, should you use your vote to make it happen? I suspect this would be a tough call to make in practice without the benefit of hindsight, but it's certainly a possibility in theory.
6. Personal GreedI'm not saying that this ought to be a motivating factor, just recognising that it could be in practice. I don't vote with my wallet when it comes to the standard tax-and-spend debate - I've voted Labour knowing that it would cost me money because I believed it was the right thing to do. But I can't guarantee I would never be swayed by an electoral bribe of heftier proportions. The obvious one that springs to mind is the right-to-buy scheme, which offered residents' discounts of up to 50% of the market price in the 1980s. Even I am not so morally incorruptible that I couldn't be swayed by a free half a house.
That's the list, although I'll add a couple of caveats: even if reasons to desert Labour present themselves, actually doing so depends on the availability of a preferable option; if they are going to lose whatever you do you might as well vote for them anyway, in the hope of limiting the scale of the defeat and keeping them in the game for next time.