Michael Solimine, who knows more about the use of 3-judge courts in election cases than anyone I know, has posted this draft on SSRN (forthcoming U Pitt. L. Rev.). Here is the abstract:

Judicial interpretations of the Equal Protection and Due Process Clauses of the Fourteenth Amendment underwent significant change, both expanding and retrenching in various ways, in Supreme Court doctrine during the Warren and Burger Courts. An underappreciated influence on the change is the method by which those cases reached the Court’s docket. A significant number of the cases reached the Court’s docket not by discretionary grants of writs of certiorari, as occurred in most other cases, but by mandatory appeals directly from three-judge district courts. This article makes several contributions regarding the important changes in these doctrines during the Warren Court (1954-1969) and the early Burger Court (1969-1976), before Congress in 1976 limited the scope of three-judge courts and the concomitant mandatory appeals. It documents the number of such cases during the time periods in question; addresses the quantitative and qualitative changes in Equal Protection and Due Process (and other) doctrines influenced, at least in part, by the availability of mandatory appeals; and normatively addresses the propriety of this influence in light of the renewed interest in reestablishing at least some mandatory appeals in current proposals to “reform” the Supreme Court.