Abortion and euthanasia are crimes, which no human law can claim to legitimize. There is no obligation in conscience to obey such laws; instead there is a grave and clear obligation to oppose them by conscientious objection. In the case of an intrinsically unjust law, such as a law permitting abortion or euthanasia, it is therefore never licit to obey it, or to take part in a propaganda campaign in favor of such a law, or vote for it (John Paul II -Gospel of Life).
Participation in the political process is a virtue, and every vote counts. Christians have every right to strive by legitimate means to shape public policy according to their moral convictions. We are all called to build a Culture of Lifevoting is among the most important ways. Political parties are not eternal, the only thing that matters is that you vote for Jesus.