It is well known that Rabbi Avigdor Miller Zatzal strongly condemned those that voted for candidates that would not uphold Torah values. Yet there were many Gedolim that had no problem voting for such candidates or endorsing them if they felt there were other benefits for the Tzibur. Coming up on this years midterm elections, Is there any Issur according to Halacha to vote for any candidates, or is it all dependent on what is overall best for us?
Almost everyone upholds some Torah values at the expense of others. For example, someone may support giving Tzedakah (a good thing) and supporting workers (in general a good thing at times) at the expense of support of positions that Torah doesn't hold of. Remember that some people who support Israel may, at times, not be ethical in office (or may turn around and go against Israel!).
Moreover, all politicians are known to lie, and what the politician will REALLY do is not known to anybody outside of very close staff.
Therefore it takes a big Rov to decide which politician is actually more in line with Torah than others.
P.S. I don't mean to bash any politicians particularly, but the Mishna does say to stay far from government!
There is an article on this topic by Rabbi Mark Dratch in which he argues that voting for e.g., a pro-abortion candidate is not a violation of "lifnei iver" because it is indirect--one is only voting for a legislator who will then vote to violate the Noahide laws. (This of course would not help for the legislator himself.) However, he concedes that there may be a prohibition of "strengthening the hands of transgressors"--מחזיקין ידי עוברי עבירה--in supporting such a candidate. (Rabbi Dratch attempts to neutralize this problem, but his reasoning is flawed.) Last, it is not true that halakhah has a specific policy proscription for everything--halakhah does not mandate what percentage of the GDP the government should spend. Certain areas, i.e., "hot-button social issues," are clearly mandated. I don't think that if a candidate is for gay marriage and abortion, the fact that e.g., he is for more headstart funding has any halakhic weight.
A person will need to weight the different issues. If a candidate is against a Jewish value in one area, but strong in an other area, then the voter will need to evaluate who's best overall. However, in many elections, one candidate or party is against far more Jewish values than the other side, so its quite easy to tell who a Jew should vote for.