When you look back on historical trends, usually you can expect a "wave year" once a decade on average. 2006 most likely happens to be that year for this decade, whereas 1994 was for the previous one.
As a proverb reads, "The only constant thing is change!" We serpentine between satisfaction with the shape of things and/or status quo and yearning for change in our system. Ultimately, the American public has fed up with the corruption and scandals the Democratic Party was tainted in in 1994, so the American public made their proclamation heard and the GOP gained a historic 52 Congressional seats and 8 Senate seats that year.
This Tuesday was another story, where the American public were unhappy with a culmination of things, especially the handling of the war in Iraq and more corruption in Congress. So the American public spoke, and the Democrats have picked up between 30-32 Congressional seats (several remain undecided) and 6 Senate seats.
That's just the nature of politics; it often has a way of fluctuating.
"If we have no peace, it is because we have forgotten that we belong to each other"