- It was demographically old. The average Tea Partier was significantly older than the mean among American voters.
- It was ideologically reactionary.
This was never a reality-based movement. It was for and by a small, insular slice of the electorate who were so self-obsessed that they couldn't see how their rhetoric plays to the real, broad American electorate. (That criticism is equally applicable to many progressive groups, by the way.)
The Tea Party may hang on poisoning Republican primaries until more of them age out of the active voter pool. But if they want to have an impact beyond the 2010 election (and little else), they'll have to develop some actual plans, not just empty slogans. There aren't any signs of that yet. Even the election of Ted Cruz, who is supposedly the intellectual of the movement, isn't particularly promising because his platform is a bunch of platitudes.
So, Tea Party, evolve or die-- the quicker the better.
"Lots of Republican voters died, and lots of Democratic voters came into being." -- The American Conservative