Church members should be given the courtesy, especially in a free society, of coming to differing conclusions without appearing to be morally in error. Exceptions would occur when, as in Nazi Germany or Stalinist Russia for example, one party stands for blatant oppression, cruel racism, persecution or fundamental denial of freedom. Where it is possible to do so, such totalitarian regimes ought to be exposed and resisted. As I see it, the Bible provides some answers to the first question. In the first place, Christians ought to understand how the political realm relates to God's rule and sovereignty.
Similar references abound.
A denominational periodical is an excellent forum for teaching in this matter. Second, contemporary Christians need to be reminded that the Bible records a long tradition of godly people taking a prophetic stance in responding to political authorities. You have set yourself up against the Lord of heaven. . . . You did not honor the God who holds in His hand your life. . . . You have been weighed on the scales and found wanting.