Might could.

source: 
LAGS
Entry: 
316
Example: 
Might could.
Modal 1: 
might
Modal 2: 
could
Gender: 
Female
Race/Ethnicity: 
White
Age: 
56
Level of Education: 
High school (Some)
Home Community, Town, or State: 
GA (Canton)
Location Collected: 
GA (Woodstock)
Year: 
1977
Relation to Addressee: 
subject to fieldworker
Medium: 
Spoken
Sentence Structure: 
unknown
Status: 
Naturalistic