I have tended to resist the arguments of friends of mine who insist that American politics have recently become uglier than they have ever been before. But an incident in Portland, Ore., on Sunday, March 25, does suggest that we may have passed a fateful turning point in our national dialogue.

On that day, several thousand antiwar protesters marched through Portland, most of them behaving the way protesters do on such occasions. According to the Portland Oregonian, however, "a handful of people set afire a uniformed effigy of a U.S. soldier and an upside-down flag." A Web site provided further details: "Photos taken by Rachel Palinkas, a Linfield College student, showed masked protesters burning an effigy of what appears to be a U.S. soldier. ... The photos showed protesters gathered around a figure wearing U.S. military fatigues and a crude skull for a head as it and an American flag were lit on fire. Other black-clad, masked protesters carried a black banner that read, 'No Gods, no country, no masters,' and a circle 'A' anarchy symbol."

Now, burning an effigy of an American soldier is not, as far as I know, something we have seen before in this country. Together with the slogan on the banner, it seems determined to push defiance of the United States and its values to the furthest imaginable extreme. Along with such recently familiar assertions as "Bush lied us into war" and "Bush lied, thousands died," it expands the rhetorical borders of political dissent into areas of irresponsibility that do seem disturbingly novel.

As I say, I have been slow to acknowledge this. Politics is a contact sport, and American history records some very extreme political utterances. Under the strain of approaching civil war, Abraham Lincoln was referred to in print as "the Illinois baboon." And earlier, John Quincy Adams denounced Thomas Jefferson as "an affront to the moral order of the universe" -- which, despite the elegance of the prose, is surely as close to a total condemnation as one person can get in discussing another.

And yet, the words and actions of many recent participants in our political debates do appear to be reaching new lows. So far, this sort of thing has occurred largely on the left, presumably because it is the left that is currently outraged by the policies of the Bush administration. (Nobody on the right has yet felt inspired to denounce Hillary Clinton with the sort of shrieking hysteria that Rosie O'Donnell sprays on Bush, to the audience's applause, on ABC's "The View.")

What is causing this? I suspect that one reason is that more people than ever before are being tempted to participate in political arguments. The teachers in our schools, and especially our colleges, have for decades been egging their students on to engage in politics -- and, of course, providing them with a (usually radical) point of view to battle for. In addition, the growth of the Internet has provided an arena in which any political viewpoint can be aired, without restraint and without any support or justification whatever. It used to be that the average person's only means of political expression was to write a letter to the local newspaper. Now he (or she) can make any assertion whatever and blare it forth electronically, nationwide.

But that is only part of the problem. In normal political discussions, a statement (or action) that is wildly over-the-top will be sharply rebuked, and the person responsible for it quickly learns not to make that mistake again. But an anonymous blogger on the Internet or a masked protester in Portland, escapes all effective personal criticism. They enjoy all the privileges of a suicide bomber, but without the suicide.

Insofar as these problems are the result of technological innovations, there is probably nothing that can be done to stop them. But the American people had better make it clear that such tactics (and assertions) are counterproductive, or our politics will soon begin resembling half a dozen female wrestlers in a tub of mud.