1. The action must be morally good, or indifferent, as to object, motive and circumstances

1. The action must be morally good, or indifferent, as to object, motive and circumstances

Catechism of the Catholic Church 1755

A morally good act requires the goodness of the object, of the end, and of the circumstances together. An evil end [motive] corrupts the action, even if the object is good in itself (such as praying and fasting "in order to be seen by men"). The object of the choice can by itself vitiate an act in its entirety. There are some concrete acts - such as fornication - that it is always wrong to choose, because choosing them entails a disorder of the will, that is, a moral evil.

Catechism of the Catholic Church 1756

It is therefore an error to judge the morality of human acts by considering only the intention that inspires them or the circumstances (environment, social pressure, duress or emergency, etc.) which supply their context.

Voting is a morally good action, but voting for any candidate, for any office, is typically to accept the good the candidate will do if elected, along with any evil he intends to do or may do. In determining the bad effects that may have to be tolerated, primacy of consideration belongs to the Non-Negotiables (life, marriage and family, religious freedom), since complex negotiable issues involve opinions about means, not essential goods/intrinsic evils.