Kevin Drum has an excellent piece for Mother Jones making the point that the Tea Parties are simply the latest iteration of a right-wing backlash that occurs every time we have a new Democratic president:

The growth of the tea party movement isn't really due to the recession (in fact, polling evidence shows that tea partiers are generally better off and less affected by the recession than the population at large). It's not because Obama is black (white Democratic presidents got largely the same treatment). And it's not because Obama bailed out General Motors (so did George W. Bush). It's simpler. Ever since the 1930s, something very much like the tea party movement has fluoresced every time a Democrat wins the presidency, and the nature of the fluorescence always follows many of the same broad contours: a reverence for the Constitution, a supposedly spontaneous uprising of formerly nonpolitical middle-class activists, a preoccupation with socialism and the expanding tyranny of big government, a bitterness toward an underclass viewed as unwilling to work, and a weakness for outlandish conspiracy theories.

What's new, as Drum notes, is the degree to which this movement has almost completely taken over the Republican Party.