Chris, at Stumbling and Mumbling, offers an either-or:
This raises a question which should be made explicit: should politics serve the preferences of voters, or their interests?
In the context of a liberal-democratic polity, the only possible answer to this is: neither one nor the other exclusively, but both. A short way of explaining the reason for this would be to say that because we live in a democracy, governments have to pay some attention to the preferences of the electorate; but because the form of the democracy is representative, governments also have to pay attention to the electorate's interests.
A government that simply ignored the preferences of those it governed might as well not bother with elections. It could in theory still be a good government (though you wouldn't bet your house on that), but even assuming it made decisions conscientiously in the interests of the population, it would be at best a benevolent despotism. Imagine a general election in which Party A promises to reform the marriage laws so as to legalize same-sex marriage (at the time illegal) and Party B argues for leaving the marriage laws unchanged. Party A then wins and leaves the marriage laws unchanged. Do the electors have any grounds for complaint? Unless you think they don't, preferences matter.
On the other hand, people elected to represent others are chosen to do a specific job, a job for which they have time that others don't and which in principle allows them to research issues in a way that not all their constituents can. The latter are entitled to expect of their representatives that they'll take the trouble to save the country from disastrous outcomes and errors of one kind and another. If something goes badly wrong during the incumbency of the government formed by Party A, the electorate can quite properly punish it next time round, and irrespective of the electorate's own preferences last time round.
The real question, therefore, is not: preferences or interests? It is: what is the proper balance or combination here?