As kids, liberals had developed close relationships with peers and were rated by their teachers as self-reliant, energetic, impulsive, and resilient. People who were conservative at age 23 had been described by their teachers as easily victimized, easily offended, indecisive, fearful, rigid, inhibited, and vulnerable at age 3. The reason for the difference, the Blocks hypothesized, was that insecure kids most needed the reassurance of tradition and authority, and they found it in conservative politics.
The most comprehensive review of personality and political orientation to date is a 2003 meta-analysis of 88 prior studies involving 22,000 participants. The researchers—John Jost of NYU, Arie Kruglanski of the University of Maryland, and Jack Glaser and Frank Sulloway of Berkeley—found that conservatives have a greater desire to reach a decision quickly and stick to it, and are higher on conscientiousness, which includes neatness, orderliness, duty, and rule-following. Liberals are higher on openness, which includes intellectual curiosity, excitement-seeking, novelty, creativity for its own sake, and a craving for stimulation like travel, color, art, music, and literature.
The study's authors also concluded that conservatives have less tolerance for ambiguity, a trait they say is exemplified when George Bush says things like, "Look, my job isn't to try to nuance. My job is to tell people what I think," and "I'm the decider." Those who think the world is highly dangerous and those with the greatest fear of death are the most likely to be conservative.
I could excerpt more, but it's probably better for you to just go read the whole thing.