With the US presidential election drawing nearer, it seems appropriate to address who a Catholic in good standing can or cannot vote for. Regarding this issue, Church guidelines fall under two categories: preferably not, and absolutely not. That is to say, there are some political issues which the Catholic Church regards as less important than others, and so, if the good policies of a candidate outweigh the bad in the “preferably not” category, a Catholic is free to vote for them, if there is no better alternative. But, if any given candidate has a policy falling into the category of “absolutely not,” the only scenario in which a Catholic may vote for them is one in which the alternative candidates support even worse violations of morality within this category. Let us examine these categories further.
Now, we will first take a look at the “absolutely not’s,” because these are far fewer in number and, hence, easily enumerated. In the document Gaudium et Spes, the Second Vatican Council had this to say on the matter , being quoted directly by P St John Paul II in his encyclical Evangelium Vitae :
Whatever is opposed to life itself, such as any type of murder, genocide, abortion, euthanasia, or willful self-destruction, whatever violates the integrity of the human person, such as mutilation, torments inflicted on body or mind, attempts to coerce the will itself; whatever insults human dignity, such as subhuman living conditions, arbitrary imprisonment, deportation, slavery, prostitution, the selling of women and children; as well as disgraceful working conditions, where people are treated as mere instruments of gain rather than as free and responsible persons; all these things and others like them are infamies indeed. They poison human society, and they do more harm to those who practice them than to those who suffer from the injury. Moreover, they are a supreme dishonor to the Creator.
Thus, whichever candidates support any of the above, can not be endorsed by Catholics (that is, if there are any viable alternative candidates who do not support the above); however, if all candidates support one or more of the things listed above, Catholics are to regrettably vote for whichever one endorses the least amount of intrinsic evils on the list. For example, a candidate who is questionably a supporter of arbitrary deportation (eg Donald Trump), is preferable to a candidate avidly supporting abortion, euthanasia, and self-mutilation (eg Hillary Clinton). And given the choice between the two, a Catholic can not morally vote in favor of the candidate who supports more abundant and greater evils—end of story.
In regards to the “preferably not’s,” these include the support of any explicit legal endorsements in favor of immoral actions which are not listed in the above “absolutely not’s,” such as divorce, sodomy, etc. A candidate who supports all of the “preferably not” issues, but none of the “absolutely not” issues, is preferable to a candidate who supports even just one “absolutely not” issue.
To summarize, a Catholic must ask the following questions when deciding who to vote for:
- Which viable candidates support no “absolutely not” issues—and if there are any, which of them supports the least amount of “preferably not” issues?
- If every viable candidate supports an “absolutely not” issue, which of them supports the least in number and severity?
 Catholic Church. Gaudium et Spes, ¶27
 P St John Paul II. Evangelium Vitae, ¶3