I think the TEA party started to die the day Palin and Bachman (and others like them) got involved. If the TEA just focused just on financials (like in the beginning) and not social ideals I believe it would be going strong for a long time. Also seems like once Democrats start blaming problems on something, that something is either dead, dying or very dysfunctional.
So, how does one maintain idealogical purity? Example. 10 folks are rock-ribbed Libertarian/Constitutionalists, and form a "movement". 100 people hear the message of limited government and financial responsibility and "join". 30 of those 100 are deeply religious fundamentalists, but are attracted to the fact that SOMEBODY is calling for reining in government. 200 of the fundies friends join because they know that fundies are are "against teh Gheyzors". Has the group been hijacked? Can ANY group that wants to form a voting majority be ideologically pure?
I think Reagan (maybe Bush) said it best when a group of gay Republicans endorsed him. He welcomed their support, saying "That doesn't mean I agree with them, it means they agree with me".
I fully support the original TEA party ideal. If a vegan joins, it doesn't make me swear off meat. If a Klansman joins, it doesn't make ME a racist, or the group a racist group.