As we approach next weeks election, Catholic voters are being inundated with messages that suggest that it would be gravely sinful to vote for President Obama.This is not necessarily true.In saying this, I want to make clear that I am not arguing that one should vote for President Obama or that there are no compelling reasons to vote against him. What I am arguing is that it is incorrect to claim that voting for Obama is necessarily sinful.Catholic moral theology understands the act of voting as a form of cooperation in the acts of others. As I noted last week in my discussion of the HHS mandate, we generally speak of two types of cooperation, formal and material. Formal cooperation is when we share the intent of the person we are cooperating with, i.e. we want their act to succeed. Formal cooperation in evil is always morally wrong.Material cooperation, by contrast, exists when our own actions enable an act which we do not directly intend. An example of material cooperation might be a decision to purchase a pair of sneakers made in a factory with substandard working conditions. The purpose of my act is to obtain footwear and not to exploit workers. Nevertheless, my act of purchasing the sneakers does play a small role in perpetuating this injustice.There are circumstances under which material cooperation in the evil acts of others can be morally licit. The general rule is that a) my own act of cooperation cannot, in itself, be evil and b) there must be a proportionate reason, i.e. the goods obtained by my cooperation must outweigh the evils and cannot be obtained through a feasible alternative (e.g. if my only alternative to buying the aforementioned sneakers was to make my own shoes).This is the framework that the U.S. Catholic Bishops and the Congregation for the Doctrine of the Faith have applied to the act of voting. As (then) Cardinal Ratzinger noted in a 2004 letter to Cardinal Francis Stafford: A Catholic would be guilty of formal cooperation in evil...if he were to deliberately vote for a candidate precisely because of the candidates permissive stand on abortion and/or euthanasia. When a Catholic does not share a candidates stand in favour 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.Those who argue that a Catholic cannot vote for a pro-choice candidate are essentially arguing that there is no good that can outweigh the intrinsic evil of directly taking innocent human life. While this may be true at the level of principle, an assessment of the goods and evils arising from the election of a particular candidate must take into account not merely the candidates philosophical positions, but also the specific policies the candidate supports and the likelihood that they can be implemented (c.f. Faithful Citizenship #37).Governor Romneys evolving position on abortion is an instructive example. In 2002, when running for governor in Massachusetts, Romney said I will preserve and protect a womans right to choose. Five years later, during his first campaign for president, he repudiated his earlier views, saying on abortion, I was wrong and that Im proud to be pro-life. After winning the Republican nomination earlier this year, however, he appeared to moderate his views again, telling an interviewer that there's no legislation with regards to abortion that I'm familiar with that would become part of my agenda. Romney quickly backtracked, but was embarrassed earlier this week when one of his spokespersons reassured a group of voters in Ohio that Roe v. Wade would not be at risk during a Romney Administration.A reasonable person surveying this history could certainly question the depth of Romneys commitment to the pro-life cause. Its not unreasonably, of course, to take him at his word. It seems clear, though, that people of good faith can disagree about the concrete impact a Romney presidency would have on abortion in the United States.A similar degree of uncertainty surrounds almost all the goods and evils that Catholics might associate with the two candidates. Romneys proposed cuts to SNAP (formerly known as Food Stamps), for example, might seem draconian and unconscionable, but there are reasons to deem such a radical restructuring of the program unlikely (hint: farming interests support the program). With respect to war and peace, its not clear that either candidate can be fully trusted to keep us out of a potentially disastrous war with Iran. The fact that the bishops may have a range of morally acceptable options for mitigating the harm of the HHS mandate blunts the force of the argument that removing President Obama is the only way to deal with the problem.It is rational to discount future benefits by the probability of obtaining them. This principle can also be applied to the promises that candidates make when running for office. Catholics acting in good faith can certainly come to different conclusions about probabilities in question, which would lead them to different conclusions about whether the proportionality test described earlier had been met. They could do this without necessarily disagreeing with the bishops that some evils are certainly more serious than others.To make these kinds of calculations is part of the work of conscience. While conscience certainly can err, we should always be wary in concluding that others are not acting according to conscience. Such a conclusion requires the deep knowledge of an individual that arises from a personal relationship. It is work best left to the confessional not the ballot box.