I anticipated someone asking a similar question, and I would propose that the answer is somewhat in the semantics of how one goes about defining politics. Roger Olson, over at Patheos, had some discussion of whether there are certain principles that can be assumed to be commonly held by all reasonable Americans. It's an interesting question in this day and age.
Now, it seems to me that the Scriptures are not much concerned with a free market economy or any number of other sacred cows of large swathes of the American electorate. Nor do I particularly care about the majority of ballot initiatives or any candidates that are running for office. Scoundrels are usually readily apparent and, again, most ballot initiatives are matters of indifference where one would be hard-pressed to prove a 'Biblical' position.
The long standing debate has been, at least for conservative Christians: do we uphold traditional morality or serve the poor? This has tended to break down as a Republican/morality or Democrat/service dichotomy. I don't see a need to be explicit from the pulpit. Most people will instantly tune that stuff out anyway (unless they think you are about to agree with their pre-conceptions).