I think I agree mostly, but disagree in part with Jonathan Chait, Jamelle Bouie, and Steve Benen when they say that Tea Partiers are really just rebranded conservative Republicans. And to go with that I mostly disagree and in part agree with Kevin Drum, who believes that Republicans are a lot more crazy now than they were in the 1990s or the 1980s.
On that last point -- it's important to remember that (if you're going to generalize from the worst of it) Republicans in the 1990s considered Bill Clinton to be a serial murderer who had traveled to Moscow for vague but somehow very relevant nefarious purposes when he was young. And while Drum notes that Rush Limbaugh has apparently taken to making cheap personal attacks on the First Lady, I can't imagine it's anywhere near the mudslinging he habitually engaged in against Hillary Clinton in the 1990s.
So why don't I entirely agree with the former group (and disagree with Drum)? Because institutions matter. Yes, Tea Partiers are almost always going to be the same group that opposed Clinton in the 1990s. But organizationally, they may well be different in important ways this time around. In particular, their eagerness to contest primary elections really does seem to matter. Granted, a few high-profile successes doesn't really mean that Members of Congress are in grave danger if they cast one bad vote. Politicians, however, are notoriously risk-averse when it comes to elections, and frequently overstate such dangers.
It may well make a big difference that Tea Partiers are an organized (or perhaps several organized) factions within the Republican coalition, and not just a bunch of rank and file ready to support the GOP. Now, how it will affect things is yet to be seen. But that's one of the things worth keeping an eye on over the course of the 112th Congress and the 2012 election cycle.