You cannot say it is a grave sin to vote for some particular party. You have to judge particular candidates, because they do not all stick to the national party platform. In Oregon, for instance, the last Republican candidate for governor went to great pains to paint himself as pro-choice.
The last time we had a presidential election, I did not think I could in good conscience vote for either of the two major party candidates. I wrote someone in who I think would actually do a good job, even though there was no chance whatsoever that he would be elected. I do not live in a swing state, however, and I do believe that a person of conscience could come to a different conclusion than I did. I don’t think it is a sin, in other words, to choose the “lesser of two evils” when you are given the choice of two seriously bad candidates.
(Please, if you think that either Mrs. Clinton or Mr. Trump walked on water, spare me the campaign rally. I’m only giving the example that there are always limited choices and it is the actual people on the ballot that count.)
Which Republican issue is on par with the Dem’s crusade to murder innocent children in their mother’s womb?
My judgement in the last presidential election was that both candidates had issues that were disqualifying on their face, without even comparing them to an alternative candidate.
As for the party I belong to, Oregon has a closed primary system, so I register based on which primary I want to vote in. It makes no difference in the general election.