This complaint to a single objective function, separately chosen by each individual voter, is one that I cannot approve (though I do see one way of understanding it).
Several in the MSM and blogosphere have argued the same over the Alternative Vote (AV), or Single Transferable Vote (STV): that it provides voting for the least unacceptable candidate rather than the most favoured candidate.
This is total bunkum.
Voting systems that provide ranking (such as STV, or its AV variant for single seat constituencies) allow voters to provide more information than is supported under First Past the Post (FPTP). Though the issue is somewhat complicated, there is an explanation of this in my comment on Samizdata
. [Note: if the link direct to my comment does not work for you, search for "April 17, 2011 10:29 AM".]
I do accept, however, and even very strongly recommend, that voters should have the option of an official abstention, interpreted as a vote against all (remaining) candidates and a call for a new election with new candidates.
Back to Richard's point, the choice of the voter should be according to what they wish, however that is determined. Whether it is love for one candidate or visceral hatred of another, or the more ordinary mixed and less extreme preferences of the vast majority, that is the private business of each individual voter. That does not stop political parties or others from noting and acting on a more general view of what or whom voters might be persuaded to vote for (ie public opinion), in their selection of candidates or of policy.
In part of my work (decision theory by machine), it is a necessary part for the best decision by machine (usually in support of purposes chosen by people) that there be a single objective function
and that the decision be made by maximising that single objective function.
There is no known better way for machines to 'think'; this is known by extensive and diligent search (including study of the parallel of the human brain and human decision-making). All attempts are futile, to avoid a single function that combines all features or characteristics into the decision: so in elections, features both of the advantages and the disadvantages of each candidate. This is because there is an implicit and unavoidable combination forced by the making of a decision.
That voters vote and vote according to their own judgement is the most important thing.
That politicians try and restrict that vote (by being against official abstentions and against AV/STV) is politicians voting for the benefit of the current political class (and hence a pretty obvious motivation). We do not need to extend that by politicians deciding that we can only vote for reasons that the politicians judge 'desirable': that is desirable benefit for them; it is not desirable benefit for us.
So people should back off wanting to constrain (or even know) the reason underlying the choice of each voter, whether it is by FPTP, AV or otherwise: that is not part of democracy. More choice, and more effective and detailed communication of that choice, would however make our democracy better, including an official abstention (and AV/STV).