After so much thought about how a Christian ought best to engage with politics, the most helpful comment I have found on the subject is this paragraph from the unanswerable Mr. Lewis:
This raises the question of Theology and Politics. The nearest I can get to a settlement of the frontier problem between them is this: that Theology teaches us what ends are desirable and what means are lawful, while Politics teaches what means are effective. Thus Theology tells us that every man ought to have a decent wage. Politics tells by what means this is likely to be attained. Theology tells us which of these means are consistent with justice and charity. On the political question guidance comes not from Revelation but from natural prudence, knowledge of complicated facts and ripe experience. If we have these qualifications we may, of course, state our political opinions: but then we must make it quite clear that we are giving our personal judgement and have no command from the Lord. Not many priests have these qualifications. Most political sermons teach the congregation nothing except what newspapers are taken at the Rectory.
C.S. Lewis, Christian Apologetics, 1945
Are you a politician? Rejoice that God has given you both goals and guidelines, but has also given you the freedom to put creative energy into the formation of effective policy. Are you a theologian? Don’t presume that your conscience is so tender, and your heart so steeped in scripture, that any opinion which seems to you to be common sense must be the only one within the boundaries of godliness. For to truly shepherd one’s flock in grace is to preach God’s word as far as it goes, and not one millimetre further.