to the question of whether it is a grave sin (or indeed any sin at all) to vote for a Democrat, it depends on the reasons for voting for that person. If one votes for a candidate because they desire an immoral policy favored by that candidate, that is a sin because it is formal cooperation with evil. But if a person votes for a candidate and does not desire that policy, but for some other reason, that can be informal mediate remote cooperation with evil, which can be allowed when there is a proportionately serious reason to do so.
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