In reading a Southern Political Report account of a Republican
challenge to the sitting GOP speaker of the Texas House (yeah, I read
that sort of thing for fun), I ran across a striking passage about
similar battles in other states. Obviously, recent experience in North
Carolina differed in details, but I think there may be something to this more-general explanation:

Division among Republican state legislators is not unusual in the
South, where federal issues provided most of the impetus for the
formation of the region?s GOP, beginning in the 1960s. With little
party-wide consensus on many state and local issues, Republican
lawmakers have often fought among themselves in Dixie’s legislatures.
For example, there have been recent splits in Alabama, between GOPers
loyal to Gov. Bob Riley?s (R) fiscal policies and those who opposed
them, and in Virginia, between suburban Republicans who want additional
revenues for services and rural GOPers who favor less spending.