The Roman Catholic Magisterium teaches that there are three fonts of morality: (1) intention, (2) moral object, (3) circumstances, and that, in order to be moral, each and every knowingly chosen act must have three good fonts. If any one or more fonts is bad, the act is immoral. If all three fonts are good, the act is moral. There are no exceptions to the three fonts of morality.
Voting ethics is not an exception to the three fonts of morality. The act of voting is subject to the same basic principles of morality as every other knowingly chosen act. If, in your act of voting, all three fonts are good, your vote is morally licit. It might not be the best possible vote; it might not be the most perfect act of voting possible. But it is moral.
Every act with an evil moral object is intrinsically evil and always immoral. Neither a good intention, nor dire circumstances can cause an intrinsically evil act to become good, or morally licit, or morally justifiable.
But voting for a person is not intrinsically evil. Every intrinsically evil act has an evil moral object, in other words, the act by its very nature is ordered toward an evil end, an end in terms of morality that is contrary to the love of God and the love of neighbor as self. But when we vote for a person, we are not voting to authorize or require any intrinsically evil act, such as abortion or euthanasia, to be committed. We are voting to elect a person to an office. While in office, that person will commit many different acts, some moral and perhaps some immoral. But even if that person commits an intrinsically evil act while in office, our act of voting for that person is not thereby made intrinsically evil.
Since voting for a person is not intrinsically evil, the morality of voting depends on intention and circumstances. It is a sin to vote with an immoral intention. For example, it is a sin to vote based on your own self-interest, to the detriment of the common good. On the other hand, the love of neighbor as self implies that you consider what is good for yourself as well as other persons. The intention of the vote should be to do as much good as possible, and to avoid harm as much as possible. But in a complex sinful world, even a good act done with good intent may have some harm in the consequences.
The first two fonts of morality must be entirely good in order to be moral. Any bad intention makes the first font immoral, even if there is some good intent with the bad intent. Any evil moral object makes the act intrinsically evil, even if there is more than one moral object and only one of the moral objects is evil.
But the third font of circumstances may be moral, even if there are some reasonably anticipated bad consequences, as long as the reasonably anticipated good consequences morally outweigh the bad. And this moral weighing or moral evaluation is always to be made in terms of the love of God, and the love of neighbor as self.
In voting ethics, to be moral the act of voting must take account of the reasonably anticipated good and bad consequences for all persons affected by the act. This moral evaluation of the weight of the consequences includes the likelihood that the candidate will be elected, the likelihood that the candidate, while in office, will do various good or bad acts, and the overall effect on the common good.
Colorado Catholic Conference: “In some moral matters the use of reason allows for a legitimate diversity in our prudential judgments. Catholic voters may differ, for example, on what constitutes the best immigration policy, how to provide universal health care, or affordable housing. Catholics may even have differing judgments on the state’s use of the death penalty or the decision to wage a just war. The morality of such questions lies not in what is done (the moral object), but in the motive and circumstances. Therefore, because these prudential judgments do not involve a direct choice of something evil, and take into consideration various goods, it is possible for Catholic voters to arrive at different, even opposing judgments.” (Colorado Catholic Conference, Moral Principles for Catholic Voters, p. 2)
However, in recent years there has been misapplication of the concept of intrinsic evil, as it applies to voting ethics, in the writings of some Bishops and of many commentators.
The fact that a candidate favors the legalization of an intrinsically evil act does not necessarily cause the act of voting for that person to be a sin. In voting for a person you are not voting for the legalization of that intrinsically evil act. A vote for a person is substantially different, in terms of morality, from a vote for a law or for an amendment to a constitution.
Also, there are intrinsically evil acts which should not be illegal. For example, lying is intrinsically evil. But if lying were illegal, the government would need to intrude on every conversation in order to determine if the crime of lying occurred. And it would be all too easy for someone with malice aforethought to falsely accuse a person of lying, causing them to be fined or jailed. But lying is generally a venial sin, unless there is something else to the lie that makes it a mortal sin.
In another example, blasphemy is intrinsically evil and always gravely immoral. Yet if blasphemy were made illegal (as it is illegal in some nations), the government would then be in the position of determining important questions of faith, questions which should be decided by the Church. Outlawing blasphemy has the effect of giving the civil courts a role reserved to the Church. And not everyone in a pluralistic society has the same religious beliefs, and so religious freedom (with its respect for the intellect and free will of human persons) would be jeopardized. Therefore, even when an act is intrinsically evil and always gravely immoral, it should not necessarily be made illegal.
The Magisterium does not teach that every immoral act should be illegal. Neither does the Magisterium teach that every intrinsically evil act should be illegal. Therefore, the mere fact that a candidate supports the legalization of certain intrinsically evil acts does not imply that voting for him is a sin. Neither does a candidates stated support for the outlawing of an intrinsically evil act imply that one must vote for him.
Certainly abortion, infanticide, euthanasia, and the destruction of human embryos should all be outlawed as serious crimes with grave punishments. But the reason that these acts should be illegal is not because they are intrinsically evil, but because the secular government has the responsibility to protect innocent life.
The Magisterium does teach that certain sins, some intrinsically evil and some not intrinsically evil, should be illegal. For the government has the responsibility to protect the population from grave harm, regardless of whether the harm is caused by an intrinsically evil act or not. Therefore, a voter may consider the issues that concern the government, and particularly the office that the candidate is seeking, on all matters that affect the common good.
Commonly it is said that war is not intrinsically evil, and so is carries less moral weight as a voting issue. But war can be intrinsically evil and gravely immoral. For example, a genocidal war is not only gravely immoral, but intrinsically evil. In another example, if the war were an unjust nuclear war, in which cities of innocent civilians would be directly targeted and destroyed, the war would again be intrinsically evil and would cause very grave harm. Given a choice between a pro-life candidate whose election will have little affect on abortion and who favors the war, versus a pro-abortion candidate whose election will have little affect on abortion and who opposes the war, no Catholic could morally vote for that pro-life candidate. For every knowingly chosen act in which the reasonably anticipated bad consequences gravely outweigh the reasonably anticipated good consequences is a mortal sin.
In acts of voting, as in all other knowingly chosen acts, all three fonts of morality must be good. The Catholic voter must have only good intentions, putting the common good above self-interest. The Catholic voter must refrain from voting for any law, referendum, or amendment that would be intrinsically unjust. The Catholic voter must consider the positions of each candidate and decide, in his prudent judgment, which candidate will best promote the common good, so that the reasonably anticipated good consequences of his act of voting will morally outweigh any bad consequences.