Note also that Obama was not seriously electorally tested in his Illinois Senate run (I don't know about his state legislature results). His opponents all had scandals.
he was a massive underdog in the Democratic primary.
Yeah, but his opponent faced domestic abuse allegations.
One of six. Granted, Blair Hull was considered the early frontrunner, but he ended up coming third. Obama just rose out of nowhere with some important endorsements and a great debate performance to take a wholly unexpected 53% of the vote.