NEW YORK (AP) - Tom Brokaw, Peter Jennings and Dan Rather - the totems of television news who informed and soothed a rattled nation following the Sept. 11 terrorist attacks - are confronting evidence that they themselves were targets for attack.

On Thursday, CBS announced that the woman primarily responsible for opening Rather's mail had tested positive for the skin form of anthrax. Last Friday, word came out the same thing happened to Brokaw's assistant, the anthrax traced to an angry letter with a reference to Sept. 11.

There was no specific threat to Jennings. But the infant son of an ABC producer who had brought her baby in to show off to colleagues _ including Jennings _ later came down with anthrax. Jennings has been tested for the disease.

"When you attack these anchors, you attack the symbols of the media establishment," said Bob Zelnick, acting chairman of the journalism department at Boston University.

Each evening news anchor has essentially been the public face for their news divisions for two decades. On any big story, ABC, CBS and NBC race to get each man in the anchor chair.

"When there is a sense of crisis, when you don't know what's going on, the television anchors calmly, dispassionately tell you what's happening," said Robert Lichter, president of the Center for Media and Public Affairs.

"The anchor's role is to steady you by projecting his calm to you, the viewer," Lichter said. "When you shake him up, you shake the viewer up."

Oddly, the three cases became public in the same order through which the anchors are currently ranked in popularity, as measured by Nielsen Media Research: Brokaw first, Jennings second and Rather third.

Brokaw became a best-selling author with "The Greatest Generation," his account of those who fought in World War II. He hasn't hidden his anger about the anthrax, or his sense of guilt that a colleague was sickened by something intended for him.

"This is so unfair and so outrageous and so maddening, it's beyond my ability to express it in socially acceptable terms," he said the day it became public.

Brokaw's test for anthrax came back negative. He has been taking the antibiotic Cipro as a precaution.

Jennings noted that he's gotten some angry mail since Sept. 11. But he hasn't been able to pinpoint any envelope or package to him that might have transmitted anthrax.

"I don't think anyone likes to think that they are a target, even though we are, all of us in journalism, very often the subject of people's ire, to put it mildly," he said on "20/20" Wednesday.

There's no hard evidence to tie the three cases together. Medically, at least, Dr. Steven Ostroff of the Centers for Disease Control and Prevention, said the CBS case "appears to be identical to the pattern at the other three news organizations."

Rather said Thursday he's trying not jump to conclusions about the cases, but said it was a "reasonable hypothesis" to suggest they may be related. He called it psychological warfare and said he would not be moved, promising a "first-class evening news broadcast" Thursday.

CBS has not located a letter or other object that may have spread the anthrax to Rather's assistant. The anchorman has not been tested for anthrax. He said he'll follow the advice of health authorities.

"I hope we're not a target," Rather said. "But since the evidence at hand indicates we are, we want to be a smart target, and use every bit of our intelligence and our experience to make it extra tough on whoever is targeting us and also every way, in word and deed, send back the message that we aren't going to make it easy, and we're not going to back down and we're not going to back up."