This uptick in the radical right predates the health care debate that is supposedly inspiring all the gun waving. Nor can this movement be attributed to a stepped-up attack by Democrats on this crowd’s holy Second Amendment. Since taking office, Obama has disappointed gun-control advocates by relegating his campaign pledge to reinstate the ban on assault weapons to the down-low.

No, the biggest contributor to this resurgence of radicalism remains panic in some precincts about a new era of cultural and demographic change. As the sociologist Daniel Bell put it, “What the right as a whole fears is the erosion of its own social position, the collapse of its power, the increasing incomprehensibility of a world  now overwhelmingly technical and complex  that has changed so drastically within a lifetime.”

Bell’s analysis appeared in his essay “The Dispossessed,” published in 1962, between John Kennedy’s election and assassination. J.F.K., no more a leftist than Obama, was the first Roman Catholic in the White House and the tribune of a new liberal order. Bell could have also written his diagnosis in 1992, between Bill Clinton’s election and the Oklahoma City bombing. Clinton, like Kennedy and Obama, brought liberals back into power after a conservative reign and represented a generational turnover that stoked the fears of the dispossessed.

While Bell’s essay remains relevant in 2009, he could not have imagined in 1962 that major politicians, from a vice-presidential candidate down, would either enable or endorse a radical and armed fringe. Nor could he have imagined that so many conservative intellectuals would remain silent. William F. Buckley did make an effort to distance National Review from the John Birch Society. The only major conservative writer to repeatedly and forthrightly take on the radical right this year is David Frum. He ended a recent column for The Week, titled “The Reckless Right Courts Violence,” with a plea that the president “be met and bested on the field of reason,” not with guns.

Image Frank Rich Credit... Fred R. Conrad/The New York Times

Those on the right who defend the reckless radicals inevitably argue “The left does it too!” It’s certainly true that both the left and the right traffic in bogus, Holocaust-trivializing Hitler analogies, and, yes, the protesters of the antiwar group Code Pink have disrupted Congressional hearings. But this is a false equivalence. Code Pink doesn’t show up on Capitol Hill with firearms. And, as the 1960s historian Rick Perlstein pointed out on the Washington Post Web site last week, not a single Democratic politician endorsed the Weathermen in the Vietnam era.

This week the journalist Ronald Kessler’s new behind-the-scenes account of presidential security, “In the President’s Secret Service,” rose to No. 3 on The Times nonfiction best-seller list. No wonder there’s a lot of interest in the subject. We have no reason to believe that these hugely dedicated agents will fail us this time, even as threats against Obama, according to Kessler, are up 400 percent from those against his White House predecessor.