The Servant of God Pope John Paul II, in his encyclical letter Evangelium Vitae, addresses at length the question of cooperation in evil which violates the dignity of innocent human life. He offers as an example the case of a legislator who has the possibility of voting for a law which would restrict the evil of procured abortion, even though it would not eradicate it completely.
He concludes that the legislator could vote for the legislation, while his own opposition to procured abortion remains clear, for his vote does not in fact represent an illicit cooperation with an unjust law, but rather a legitimate and proper attempt to limit its evil aspects. In an analogous manner, as voters, we are often faced with a choice among candidates who do not fully oppose unjust laws. In such a case, we must choose the candidate who will most limit the evil effects of unjust laws.
But there is no element of the common good, no morally good practice, which a candidate may promote and to which a voter may be dedicated, which could justify voting for a candidate who also endorses and supports the deliberate killing of the unborn, euthanasia or the recognition of a same-sex relationship as a legal marriage. The respect for the inviolable dignity of innocent human life and for the integrity of marriage and the family are so fundamental to the common good that they cannot be subordinated to any other cause, no matter how good it may be.
