Just suppose that establishment Republicans, knowing that it is their hard right base that is the most discontent in the electorate (after all it was a Republican who gave us the evil TARP), acquiesce to the "throw the bums out" cries and take what is basically a protest movement and turn it into a quasi-political party. Now they don't do this all that overtly, and in some instances they may even protest over the candidates this group puts out, but behind the scenes they know that the movement is better off under their control than it is running wild.
They also know that this movement has the capacity to put forth some fairly extreme candidates, mainly because some of the movement members are, in fact, fairly extreme. All the better for establishment Republicans: it's like allowing your four year old to to pull the cat's tail...some lessons need to be learned the hard way. Getting the extreme wing out front and center, with tacit support, gives the larger American electorate the ability to see just what "hard right" really means. These candidates may fail, and the establishment Republicans get a de-facto purge without actually having to do any of the dirty work themselves. Well at least not in the limelight.
Could some of the movement candidates actually win? Sure. But that's okay as well. I think the establishment Republicans need poster children for their far, far right brethren, and since Rick Santorum was discovered to be an ineffective buffoon, and Rush Limbaugh prefers to earn his millions honestly, a replacement or two is called for. They key though here is control: who really controls the movement? Is it really all that "grass roots"? Who benefits from the success of the movement? Who benefits from its failure?
Here's what I think...
Q: Who really controls the movement?
A: The established Republican party. Remember, people like Jim Demint and Michele Bachmann existed long before tea was being served.
Q: Is it really all that "grass roots"?
A: It was, once. Now just look at who is throwing money into it.
Q: Who benefits from the success of the movement?
A: Establishment Republicans. In seniority-based systems, the new guy/gal seldom gets to call the shots anyway. Establishment Republicans get to claim all manner of victory if the movement wins. They get to move some rotting corpses out of their own party, people who probably should have left a long time ago anyway.
Q: Who benefits from its failure?
A: Establishment Republicans. The dialogue works something like this: "Hey, we told you O'Donnell was too extreme to win in a general election. Next time listen to your party leaders."
In the limited bits of political calculus that I understand, it seems to me that the Tea Party isn't all that bad of a deal for establishment Republicans.