A moral person should never knowingly vote for any kind of evil.
Yes, in Heaven, or any other pefect place, you'd never have to. But down here in the real world, you sometimes do.
To show how ridiculous that high sounding statement is, answer this: Would you ever vote for any candidate that had ANY position whatsoever that you felt was wrong? if you answer yes, you are doing what you claimed you would not do above, and if you answer no, you'll never, ever vote in your lifetime.