WASHINGTON  Within minutes of the first reports Saturday that Representative Gabrielle Giffords, an Arizona Democrat, and a score of people with her had been shot in Tucson, pages began disappearing from the Web. One was Sarah Palin’s infamous “cross hairs” map from last year, which showed a series of contested Congressional districts, including Ms. Giffords’s, with gun targets trained on them. Another was from Daily Kos, the liberal blog, where one of the congresswoman’s apparently liberal constituents declared her “dead to me” after Ms. Giffords voted against Nancy Pelosi in House leadership elections last week.

Odds are pretty good that neither of these  nor any other isolated bit of imagery  had much to do with the shooting in Tucson. But scrubbing them from the Internet couldn’t erase all evidence of the rhetorical recklessness that permeates our political moment. The question is whether Saturday’s shooting marks the logical end point of such a moment  or rather the beginning of a terrifying new one.

Modern America has endured such moments before. The intense ideological clashes of the 1960s, which centered on Communism and civil rights and Vietnam, were marked by a series of assassinations that changed the course of American history, carried out against a televised backdrop of urban riots and self-immolating war protesters. During the culture wars of the 1990s, fought over issues like gun rights and abortion, right-wing extremists killed 168 people in Oklahoma City and terrorized hundreds of others in Atlanta’s Centennial Olympic Park and at abortion clinics in the South.

What’s different about this moment is the emergence of a political culture  on blogs and Twitter and cable television  that so loudly and readily reinforces the dark visions of political extremists, often for profit or political gain. It wasn’t clear Saturday whether the alleged shooter in Tucson was motivated by any real political philosophy or by voices in his head, or perhaps by both. But it’s hard not to think he was at least partly influenced by a debate that often seems to conflate philosophical disagreement with some kind of political Armageddon.