There are no Church teachings on how Catholics have to vote. In fact, there can't be any Church teachings on how Catholics have to vote, now or ever.
What the Church can and does teach (to some extent) is how Catholics should vote, or more generally how they should go about voting. The Church doesn't say, "All Catholics must...," but, "Everyone with a well-formed conscience will...," which teaches us what having a well-formed conscience implies and whether we have one.
It's true that, at various times and in various ways, Church authority is invoked to direct or order Catholics to do certain things. But directions and orders are not teachings.
In an attempt to "vote with the mind of the Church," as it were, I think this distinction is important. Not for its own sake -- the effective difference between "you should" and "you must" isn't very large for someone inclined to listen regardless -- but for the sake of answering the... ah, inexperts who consider statements like, "I don't let the Pope tell me how to vote," sound arguments.