http://www.nathannewman.org/EDIN/.election/.1994/.1994anal/.WDB.html
1994 was an abrupt, brutal and fundamental change, in which Democrats lost 56 USHR seats (35 incumbents and 21 open seats) to for open-seat losses for the Republicans. In sheer volume of turnover, 1994 ranks fifth of 21 off-year elections since 1918 -- just a shade behind 1946.
I suppose you have a problem with my hypothesis?
Yes, the GOP took hold, but Clinton gave away and sold our secrets to the ChiComs and more. Ge passed all kinds of EOs, which could NOT be undone by President Bush. Clinton's true legacy is 9/11! Without his presidency, that wouldn't have happened.
I can give you many other overriding examples, but you really should know it, without my having to enumerate them all.