Sometimes, as in the case of the referendum on the alternative vote, it is not at all obvious that there is one "right" way to vote and a "wrong" way to vote. The decision about which way to vote is then more a question of prudential judgement rather than of immediately moral judgement. We do nevertheless have a duty, to the best of our ability and making use of the forms of social communication, to inform ourselves about the question and come to a prudential judgement. And then to go out and vote.
Thinking Faith has an article which looks at this in more detail.
This would seem to rule out the idea of our finding a simple ‘yes’ or ‘no’ to the question in hand, but we should not lose all hope of finding guidance, because the preceding paragraph states:And their conlusion:
"The Church values the democratic system inasmuch as it ensures the participation of citizens in making political choices, guarantees to the governed the possibility both of electing and holding accountable those who govern them, and of replacing them through peaceful means when appropriate. Thus she cannot encourage the formation of narrow ruling groups which usurp the power of the State for individual interests or for ideological ends. (John Paul II, Centesimus Annus n.46)"
That one paragraph offers us, at least, some principles – some criteria which we might apply when considering the merits of different voting systems. Two of the principles are stated quite explicitly here: participation and accountability. A third is suggested by those final words about the undesirability of narrow ruling groups usurping power for their own interests – the principle of the common good, which is found throughout Catholic social teaching....
All in all, these considerations do not lead us to a very emphatic conclusion on the question of whether the Church’s teaching would encourage us to vote ‘yes’ or ‘no’ to the introduction of the Alternative Vote. The Church’s teaching has given us clear criteria to judge by – the difficulty is that the evidence about how well AV might meet those criteria is extraordinarily mixed.I expect that, if the referendum approves a change to the alternative vote system for parliamentary elections, the impact will be very different in different places. In "safe seats" used to having a large majority for one of the major parties it will probably not make much difference to the final outcome. In "marginals", where majorities are small and the seat changes hands from time to time, the impact of the alternative vote system might well lead to a different outcome. There is a potential for inappropriate minority parties to gain an undue influence. This differentiation of impact is of the nature of much legislation.
My own sense is that the introduction of an alternative vote system will, in general, make those standing for election more sensitive to wishes outside of the mainstream of political stances. In marginals this will be more acute than in safe seats, but I suspect it will still occur in safe seats. [In Barking and Dagenham, those council wards in which the BNP have done well, even at one point to the extent of having councillors elected, have not shown the BNP gaining anywhere near an overall majority; so I am not convinced that such parties would gain from an alternative vote (indeed the BNP stance is to oppose AV).] This gives Christians a greater opportunity to influence for the good in the political sphere - and, of course, a consequently greater duty to go out and vote in order to exercise that influence.
And, besides, if Mr Cameron is against it it must be a good idea (oops, political bias showing).