It is neither "prudent" nor "permissible" to vote for a lesser evil. Sorry. That's false ends-justifies-the-means moral reasoning. It is NOT Catholic.
The principle is that if one ONLY has two choices of evil, he must choose the lesser evil. But "voting" really isn't that....because you can choose NOT TO VOTE, or to vote for a WRITE IN CANDIDATE....at least in the U.S.
Just so I understand what you're saying:
People are arguing that there are only 2 choices:
1. vote for evil candidate X
2. vote for evil candidate Y, who is supposedly slightly less evil than candidate X (because it's only way to keep out supposedly even worse candidate X)
Whereas you are saying that is incorrect, in that we have more choices,
1. vote for evil candidate X
2. vote for evil candidate Y, who is supposedly slightly less evil than candidate X
3. don't vote at all because both X & Y are evil
(and our voting system is a complete fraud anyway)4. write someone else in
i.e. It's not like someone is putting a gun to our head, saying "you must vote for evil candidate X or Y."
Is that what you're saying above?