I don't think we'll know much of anything until after the first of the year, but I agree that this time, things at least SEEM different.
I don’t think it’s really that unique. The most recent examples to look at would be cases of the incumbent party vacating the seat, so 2008, 2000, and 1988. What seems to happen is that the opposition entertains more “unorthodox” candidates before settling on the consensus nominee. In 1988 Jesse Jackson was making a lot of noise for the D’s; in 2000 McCain was the darling of many conservatives because of the “straight talk”, issues be damned. Obama was a bit different as he was not the favorite of the establishment, but he was far from an outsider - the best comparison for him would probably be like a Rubio. (At least as how the establishment relates to him. I fully understand how most people around here feel about him, but that’s not really the point.)