When the pendulum swings too far one way (GOP, 2002-2006) it always swings back the other way, or falls back in the center depending on the amount of momentum.
I suspect that after Barack Obama is elected president, he'll spend his first two years pushing for liberal programs and greenlighting whatever congress wants. Then, if he wins a second term, the house will return to Republican control, the Senate will remain Democratic, and spending will be reigned in. New spending will be limited thanks to gridlock, and President Obama will reluctantly follow.
This is of course assuming the GOP has decent leadership and returns to being the party of smaller government.
Gridlock is a beautiful thing. When neither side gets anything done, the taxpayers win.
