According to Jonathan Haidt, liberals tend to be much higher than conservatives on a major personality trait called openness to experience. People who are high in openness to experience crave novelty, variety, diversity, new ideas, and travel. People who are low on it like things that are familiar, that are safe, that are dependable. Psychologist Robert McCrae observed, "Open individuals have an affinity for liberal, progressive, left-wing political views" (they like a society which is open and changing) "whereas closed individuals prefer conservative, traditional, right-wing views."
In an excellent TED talk, Haidt points out that when people all share values and morals, they become a team, and once you engage the psychology of teams, it shuts down open-minded thinking. When liberals lose an election, they try to explain why half of America voted for the "wrong" team. They think the nation must be blinded by religion or by simple stupidity. If conservatives lose an election, they suspect that those who voted the "wrong" way weren't voting with their intellect but were motivated by short-sighted selfishness ("free stuff").
However, if we think that half of America votes the wrong way because they are somehow blinded, then we're trapped in a particular moral matrix, we're lost in our own schema.
Zen master Seng-ts'an said "If you want the truth to stand clear before you, never be for or against. The struggle between for and against is the mind's worst disease." Unfortunately, it's a disease that many of us have caught.