It is too difficult and time-consuming to make a “fully rational” voting decision, so we use heuristics (“rules of thumb”). In particular, we use:
The nature of the times heuristic: When times are good, you vote for continuity. When times are bad, you vote for change.
The identification heuristic: You are more likely to vote for people you identify emotionally with, with people who, you sense, “get you.”
–Francisco Toro (via Evangeline White)