I thought it was a good idea, but I might could have been wrong about that.

source: 
Mishoe
Entry: 
68
Example: 
I thought it was a good idea, but I might could have been wrong about that.
Modal 1: 
might
Modal 2: 
could
Gender: 
Female
Race/Ethnicity: 
White
Age: 
20s
Level of Education: 
Unknown
Home Community, Town, or State: 
Unknown
Location Collected: 
SC/ NC (Unknown)
Year: 
c1990
Relation to Addressee: 
female to group
Medium: 
Spoken
Sentence Structure: 
1.1
Status: 
Naturalistic