...[O]n the far right, Glenn Beck and his allies cast President Obama as the central figure in a conspiracy against America itself, fueling participation by the most extreme 10 percent or 15 percent of the electorate.

Their crackpot ideas, as the historian Sean Wilentz documented in the New Yorker recently, originated in the 1950s and '60s, in the paranoid theorizing of the John Birch Society. But whereas responsible conservatives such as William F. Buckley Jr. denounced the Birchers and the rest of the lunatic fringe back then, Republicans this time are riding the radical wave. In some cases (think Sharron Angle in Nevada), the extremists are their standard-bearers....

...The Democrats are weeks away from a midterm thumping that wasn’t supposed to happen, and the liberal mind is desperate for a narrative, a storyline, something to ease the pain of losing to a ragtag band of right-wing populists. Something that explains the Tea Parties — and then explains them away....

...THE TEA PARTIES ARE JUST THE JOHN BIRCH SOCIETY ALL OVER AGAIN. In a recent issue of Mother Jones magazine, Kevin Drum argued that the Tea Parties are nothing new: whether the president is F.D.R., L.B.J. or Bill Clinton, a batty conservative populism flourishes “whenever a Democrat takes over the White House.” Writing in The New Yorker, the historian Sean Wilentz made a similar point, linking Glenn Beck’s daffier ideas (and the Tea Partiers who love them) to the cold war-era paranoias of the John Birch Society.

These parallels are real. But there’s a crucial difference. The Birchers only had a crackpot message; they never found a mainstream one. The Tea Party marries fringe concerns (repeal the 17th Amendment!) to a timely, responsible-seeming message about spending and deficits. Which is why, for now at least, it’s winning over independents in a way that movements like the Birchers rarely did....