A short while ago i wrote some thoughts about Christians and politics here.
Here's a short quote from it:
"I would say that I believe there is a great need for Christians to involve themselves in politics. Christians who set Christ first in their affections & spend more time reading His Word than they do any constitutions. Who devote themselves more to reaching the lost with the Gospel than with canvassing on the doors for their party & who realize that this is all a temporary business!"