The 2006 midterm election in the United States has been almost
universally described as an overwhelming victory for the Democratic
Party.  But in addition to achieving majority status in both chambers
of Congress, Democrats successfully defended every single House and
Senate seat.  In other words, every single Democrat in Congress who
ran for reelection, won reelection, and every Democrat in Congress who
retired in 2006 will be succeeded by another Democrat.  The shutout of
the GOP also extended to the 36 gubernatorial elections that took
place this year.  I have seen some media outlets claim that this
result is unprecedented in American history, while others imply that
it has occurred before.  My question is this: is such a shutout truly
unprecedented, and if not, when was the last time it occurred?