Key points are not available for this paper at this time.
John R. Johannes, John C. McAdams, The Congressional Incumbency Effect: Is It Casework, Policy Compatibility, or Something Else? An Examination of the 1978 Election, American Journal of Political Science, Vol. 25, No. 3 (Aug., 1981), pp. 512-542
Johannes et al. (Sat,) studied this question.