Writing in the Washington Monthly ‘Political Animal’ blog, Ed Kilgore argues persuasively that the tea party is not the sole or necessarily the primary cause of “The Slow But Very Steady Demise of Republican Moderates“. Noting that “The steady drift to the Right in the GOP Senate Caucus is more a matter of generational replacement than of “purges,” supplemented by the concentration of “conservatives” in states relatively invulnerable to general election swings,” Kilgore explains:

…Some political observers still seem to think the current ideological rigidity of the Republican Party is a sudden phenomenon created by the startling appearance of a Tea Party Movement in 2009. The often-unstated premise is that the GOP can be returned to its senses by a healthy general election defeat or two–or perhaps a win if it forces Republicans to come to grips with the responsibilities of governing.
Sorry, but I see no reason to think any sort of “course correction” is inevitable. The latest ideological lurch of the Republican Party came after two consecutive cycles in which the party was beaten like a drum. But it also drifted to the right during every recent Republican presidency; there’s a reason that GOPers were muttering about the “betrayals of conservative principle” their chieftains were exhibiting during W.’s, second term, his father’s one term, and yes, even Ronald Reagan’s second term. Like the tax cuts for the wealthy that are their all-purpose economic policy proposal, a shift to the right has become the all-purpose response to any political development over more than three decades. The Tea Party Movement is simply the latest incarnation of the conservative movement, which has been thundering against RINOs all the way back to the days when they actually existed.
There’s nothing new here, folks. There may be limits to how far the ideological bender of the GOP can be taken, but the idea that it will end next year or the year after is completely without empirical foundation.

It’s a useful insight, especially for Dems who may be entertaining the delusion that the Republican party will likely recover a semblance of the bipartisanship of earlier decades, once the tea party dissolves. More likely it will morph into something else, equally, or even more obstructionist.