1. In the present circumstances, it is a strict obligation for all those who have the right to vote, men and women, to take part in the elections. Whoever abstains from doing so, in particular by indolence or weakness, commits a sin grave in itself, a mortal fault.
2. Each one must follow the dictate of his own conscience. However, it is obvious that the voice of conscience imposes on every Catholic to give his vote to the candidates who offer truly sufficient guarantees for the protection of the rights of God and of souls, for the true good of individuals, families and of society, according to the love of God and Catholic moral teaching.
From this speech, Pius XII sets forth a specific situation where Catholics are morally required to vote. One may conclude that in the event one was presented with only one candidate who was truly Christian in his platform, that Catholics would have a moral obligation to vote for such a candidate.
In our upcoming election, it is my current opinion that we have no truly Catholic candidate. I concede that we have (or had) candidates who are Mass attending Catholics, who seemingly stand on pro-life / anti-abortion platforms. On other areas of Catholic Moral teaching, the stances of these candidates have been less certain if not in specific contradiction. We are seemingly left to compare and choose from what is popularly referred to as the "lesser of the evils."
Morally speaking the defense of innocent life, defense against the horrors of abortion, has highest priority when comparing candidates. End of life issues such as opposition to euthanasia comes in close second. Other topics such as the regularization of homosexual activity, unjust wars, care for the impoverished, and materialistic economic policy are also topics of importance, but are significantly outweighed by the proclivity of this society to destroy innocent human life.
Then Cardinal Joseph Ratzinger in his 2004 memorandum "Worthiness to Receive Holy Communion" wrote:
A Catholic would be guilty of formal cooperation in evil, and so unworthy to present himself for Holy Communion, if he were to deliberately vote for a candidate precisely because of the candidate's permissive stand on abortion and/or euthanasia. When a Catholic does not share a candidate's stand in favor of abortion and/or euthanasia, but votes for that candidate for other reasons, it is considered remote material cooperation, which can be permitted in the presence of proportionate reasons.Proportionate reason can speak to the topic of voting for a "lesser evil". Proportionate reason can also come into play where one candidate holds to an immoral view that far outweighed the grotesqueness of abortion. Currently, it is difficult to imagine a situation that is more demanding than the millions of innocent lives being taken.
While voting for a true "lesser evil" is permitted in certain circumstances, it is difficult to state that the Church has taught that one is morally required to vote at all in a situation where none of the candidates "offer truly sufficient guarantees for the protection of the rights of God and of souls, for the true good of individuals, families and of society, according to the love of God and Catholic moral teaching."