The thing that seems to be lost on a lot of people is that the "Tea Party" is not a party at all. It's a decentralized grass roots movement of people who have seen the state of our nation and have launched a public backlash. It's not comprised strictly of "social conservatives", "fiscal conservatives", or "foreign policy conservatives", yet it has elements of all of these disparate groups. It seems to me that it's truly the philosophical heir of the "Reagan Revolution".
The attempt to define this movement by any one part is to not understand it at all. There's a commonality among all of these disparate factions born from the government excesses that we have witnessed during the recent past and the abject dismissal of the will of the people. The reason that it's gaining traction is that its simple principles of common sense resonates with a growing number of people in this country.
The "country club Republicans" resent this, but they resented the Reagan Revolution as well. As for the Democrats, they feel as though they have cornered the market on "populism" by playing a decades-long game of class and race warfare. One of the effects is that there are a lot of people being unmasked and, increasingly, people are not liking what they are seeing.
Are there a few nutcases involved in this movement? Well, of course there are. There are a few nutcases involved in any movement, and this one is no different. There will always be those who glom onto a movement with their own agenda. That said, this movement is remarkably self-policing because it is comprised of "grass roots" Americans, many of which who are becoming involved in the political system either for the first time, or returning to the fray out of concern for their country. These aren't extremists voicing radical themes; they're people who are giving voice to doubts many of us have regarding the health and long-term viability of our republic.