Why did Obama nearly win Missouri?

[MarkD]

I'll point out some of the same information as jamespol did above, but I'll discuss more of the details.

Jay Nixon won the Governor's race by nearly 19 points.
Democrat Robin Carnahan won the SoS race by 26 points.
Republican-turned-Democrat Chris Koster won the Atty. Gen. race by nearly 6 points.
Democrat Clint Zweifel won the Treasurer's race by by over 3 points.
Democrat Sam Page (now the C.E. of St. Louis County) lost the Lt. Gov.'s race by under 3 points.

And yes, even in that election, there were still tens of thousands of rural conservadem voters that have since turned into loyal Republicans. Even though Republicans had a majority in the state House, there were still several conservadem state reps elected from rural districts.
So there may have been a kind of reverse-coattail effect going on.