At the presidential level, we see the more-or-less constant alternation of Republican and Democratic control, complicated only by Democrats relinquishing the presidency a cycle too early in 1980. But at the sub-presidential level, we don’t really see much evidence for the “classic” re-alignment narrative: We see no movement toward the GOP in either 1968 or 1980, nor do we see emerging Democratic strength around 1992.
If anything, there’s a lurch toward the Democrats during the 1950s, when Dwight Eisenhower, the paragon of GOP moderation, was president. The 1968 and 1980 elections result in very little movement toward Republicans at the sub-presidential level. Then in 1994, we actually see a sustained shift toward the GOP.
For all the talk of the Republicans’ weaknesses, even after the disastrous 2005-to-2009 time period, they actually wound up with a showing that was about at the midpoint for the entire 1945-to-2013 series. In fact, their overall position in 2009 was stronger than it was during all but four years of the Reagan/Bush41 time series.
If you’re trying to find a pattern here, it is probably this: Parties always end up in worse shape at the end of holding the presidency than at the beginning. Whether it is House seats, Senate seats, statehouses, or governorships, the party in power almost always finds its fortunes sagging after taking control of the White House.