The Church’s argument for the Lesser of Two Evils candidates is simple and obvious: Better the corrupt guy who may accidently do some good or at least not be as passionate about doing evil than the guy bound and determined to do grave evil. Anybody can see the reasonableness of this.
The problem comes in when both candidates are, practically speaking, committed to intrinsic grave evils and, practically speaking, will see to it that those evils continue, even though one of them may do so with a sad face.
Zippy Catholic lays out the problem with supporting that when the Church makes the justification “proportionate reasons for remote material cooperation with grave evil”:
One outcome-independent consideration I’ve discussed before is that for most people, voting involves formal cooperation with evil. So even when you, dear reader, are well-formed enough to avoid formal cooperation with grave evil in voting, there is the scandal that most people are not. I’ve also argued that because the effect you have on the outcome is literally negligible, the particular outcome you prefer cannot be invoked as proportionate reason to materially cooperate with grave evil, especially when that grave evil is some form of murdering the innocent.
The highlighted point is, I think, very compelling. It’s this: the mathematical reality is that because the impact of your vote is, quite literally, utterly negligible to the outcome of the election, there can *never be* a proportionate reason to cast it for grave intrinsic evil since the impact of the vote on you will always vastly outweigh the impact of your vote on the election.
One of the ironic testimonies to the truth of this is the fact that those who object to the choice to support candidates who advocate no grave intrinsic evil virtually always do so by a) trying to argue that avoidance of grave intrinsic evil worthy of the everlasting fires of hell is “perfectionism” and b) by those same people routinely labelling those who wish to avoid the everlasting fires of hell as prissy self-regarding narcissists. Such arguments then typically go on to boasting about the critic’s own “realistic” willingness to manfully roll up one’s sleeves and “get our hands dirty” by supporting grave evil — oblivious to so much as the possibility that such a pose of manful courage is itself a form of self-regarding narcissism. Those who strike that pose should consider a) the fact that it is anything but “realistic” to imagine that one vote out of millions has any real impact on the outcome of a presidential election. They should also reflect on the fact that the rhetoric they use to hail themselves as “courageous” and those who take another path to limiting evil as fools for being concerned about grave intrinsic evil goes a long way to persuade some of us that Zippy has a very important point about how supporting candidates who advocate grave, intrinsic evil is a game not worth the candle since the effects on the voter seem to vastly outweigh his vote’s effect on the election.