I know people who like to go down a list of where the candidates stand on the issues and then decide on who to vote for. At first glance this sounds sensible.
However, ALL candidates shift their position on major issues over time. Just because a candidate takes a particular stand on an issue today, doesn't mean that it is the stand they have taken in the past and is not necessarily the stand they will take in the future.
Prime example from the past. George Bush Senior with his "Read my lips no new taxes", how much clearer can an stand on an issue be? In the end he changed his position (you can make a case that it was for a legitimate reason, but none the less - he took a stand and didn't follow through).
BOTH current Presidential Candidates have shifted positions over the years on many issues - they all do it. The trick is to examine their history, what type of person they are, and why have they changed their position.
I would never want to elect a person who was so locked into their positions that they would never change, not matter what the situation. But I also want a person who has some type of belief system that is largely compatible with mine.
People do evolve over time (Hillary was a member of College Republicans and Reagan used to be a Democrat), and situations do change (Many isolationists changed their position on entering the war after Pearl Harbor was bombed).
A simple check list of where the stand today only gives you one small glimpse into the candidate. You need to look at their current stands - their prior stands, the actions they have taken (voting records etc.) along with a general idea of what type of person they are. This along with many other factors should be taken into account when selecting whom to vote for.