The Republicans Tommy Pope and Ralph Norman advanced on Tuesday to a May 16 primary runoff for the U.S. House seat in South Carolina vacated by Mick Mulvaney, now director of the Office of Management and Budget. The winner of the runoff will face Archie Parnell, who won the Democratic primary, on June 20.

Unlike other recent special elections, the race in South Carolina has drawn relatively little attention from either national party. The district was redrawn to heavily favor Republicans after the 2010 elections, and Mr. Mulvaney won his three re-election campaigns easily.

So far, national Democratic activists appear to have their hands full with special elections in Georgia and Montana, and party strategists on both sides believe it would take an unexpected event to make the South Carolina general election truly competitive.