You are too young to remember 1964 and 1968. There is no excuse for not remembering 1976 or 2008.
I was too young to remember 1976, I wasn't even born yet!
As for 2008, are you saying that the only reason why people voted for Obama was because he wasn't Bush, and had nothing to do with the empty promises he made, or the color of his skin?
In my honest opinion, yeah, I really think at least the white people who voted for Obama did so mostly because he wasn't Republican. If you recall, like with Trump, our media did a really, really good job at blaming Bush for everything from 9/11 to natural disasters like hurricanes, or the reaction to them, even though later it was found that was much more in the lap of the governor of Louisiana than it was Bush. But, who owns the media, wins.
I think it's been made more than clear via focus groups and talking heads since that blacks mainly voted for Obama simply because he was black (and that big, fat D next to his name, they seem to think that's going to help them, too, against all evidence to the contrary).
Plus, our political system is really cyclical, "grass is greener" syndrome and all that. It's very common for Republican led House or Senate to sway the other direction after 4 years...and vice versa. People always just seem to think a "different" politician is going to change things for them...whether it's their party or their race or their gender, it all ends up being the same people once they get in office. Like how feminists seem to think having a female president is the cure to everything. It will just end up being some other person, bought by focus groups, telling us lies...but with different body parts.