What happened in 2006 was the GOP lost their majority in the mid-terms. Because the reality of our elective system is that the two parties just trade back and forth. Same reason the dems won in 2008. For well over 100 years, with a handful of exceptions, is one party gets the White House for 2 cycles, they lose Congressional seats in the mid-terms, then they trade. Lather, rinse, repeat. There are no permanent majorities, demographics are not destiny, and nothing really changes cause the parties don’t actually stand for anything.
You may have a point. I now suspect things work differently from what we have always been led to believe.