For class, I’ve just started reading David Mayhew’s Divided We Govern. In the preface to the 2nd edition, Mayhew notes that of the eight possible permutations of partisan control of the House, Senate and presidency, the current set up with Republicans controlling only the House hasn’t occurred since right before the South seceded from the Union:
If the presidency, House, and Senate are arrayed in order, the possibilities are respectively DDD, DDR, DRD, RDD, RRD, RDR, DRR, and RRR. How many of those eight patterns have appeared since 1980? The answer is now six, which shows the surprising versatility of the regime that has unfolded in recent decades. The only exceptions are DDR (The Republicans have not controlled just the Senate since 1885-1889) and DRD (the Republicans have not controlled just the House since 1859-61).
In a footnote, Mayhew admits that a graduate student at the University of Wisconsin corrected him that technically the Republicans controlled only the House “for a couple of weeks in January 2001, between the start of the new 107th Congress and the inauguration of George W. Bush.” But other than that narrow technicality, the make up of the current governing regime is unique in the modern era.