Totally agree because I really thought Romney had a good chance in light of the economy but I think it ended up being what you said plus not wanting a Romney administration and choosing the "lesser of two evils."
I think a lot of it may have been fear of the GOP extreme "Tea Party" faction.
After all, in 2000 GWB promised to govern from the center and derided "nation-building", yet let himself be guided by the right-wing into massive spending/deficits and a misdirected war...