Name recognition is his biggest obstacle in the primaries and possibly the general election.
I don't understand why people think this is an issue in the general election. Anyone, by virtue of being nominated for president by one of the two major parties, becomes a household name, with ~100% name recognition among voters. Do you think more than a handful of voters outside Arkansas had any clue who Bill Clinton was in 1989? Yet by 1992, everyone knew who he was, since the media and the culture at large were talking about the election every day.
True. Same with Jimmy Carter, who nobody outside Georgia knew before he won the nomination in 1976. Obama was also not well known outside of Illinois before 2007.