Via Mickey Kaus, here’s top election analyst Charlie Cook illustrating the subjectivity of defining an electoral “wave” (just like mandates):

Do the math: An 11-point Democratic lead on the generic ballot test, minus 5 points for the gauge’s Democratic skew, translated into a 6-point Democratic victory. When the 6-point Democratic popular vote win is measured against the GOP’s 5-point win in 2002 and its 3-point win in 2004, it clearly constituted a wave.

Kaus rightly slams Cook for using a one point difference in the national margin to draw the line between a wave and non-wave:

Wow. So in 2002, a humdrum, non-wave election, the GOP won by 5 points. But this year, in a “wave election that rivaled the 1994 tsunami,” the Dems won by 6 points. See? No wave: 5. Wave: 6! Cook has a powerful way of putting things.