U.S. bishops of the Catholic Church say: "Political choices may affect individual salvation." They have issued guidelines for every presidential election in the past three decades. They do not endorse specific candidates but do make fighting abortion a priority in political decisions. The statement says "it must always be opposed."
The bishops also oppose same-sex marriage, embryonic stem cell research, and euthanasia. For Catholics who want to vote contrary to church teaching that's allowed, but only for "truly grave moral reasons, not to advance narrow interests or partisan preferences." In other words, you decide, but be careful.