Republicans have been incredibly lucky since 2002 and 2004. Don't any of you remember in 2000, at the height of Clinton's obvious stupidity and cowardice, we still lost 5 Senate seats?
I'm sure nobody else will agree with me, but the biggest reason Republicans lost so much popularity is because gas prices stayed too high, too long. Yeah they came down over the last 3 months, but by then, the damage was already done.