I am opposed to Barack Obama because he is clearly a committed liberal and, based on his record, tends towards socialist fascism (but, international rather than nationalistic). Here, from his memoir, is something that makes me very nervous about him (from the blog Roger's Rules):

Recalling in his memoir how he dealt with his mother when she confronted him about drug and alcohol use in high school, he confides a bit about his methods: “I had given her a reassuring smile and patted her hand and told her not to worry, I wouldn’t do anything stupid. It was usually an effective tactic, another of those tricks I had learned: People were satisfied so long as you were courteous and smiled and made no sudden moves.”

How do we know that he is not just playing us now, and will reveal his true intentions after he is elected? By the way, his tactic wouldn't have worked with my Mother; maybe that is why I am skeptical of him.