In a full-page announcement, New York's Village Voice recently invited one and all to come to the Great Hall of Cooper Union -- where Abraham Lincoln made the speech that caused his bid for the presidency to catch fire. I have been at many debates and discussions there, some fiery, but always the clashing ideas could be heard.

This time Democratic Gov. Robert Casey of Pennsylvania was to deliver the speech the Democratic Party would not allow him to make at its "unified" convention. Casey is a liberal Democrat. He has created and expanded, for example, a program providing crucial medical services to low-income pregnant women and young children, and he was responsible for the first increase in minimum teacher salaries in the state in a quarter of a century.

But Casey failed to pass the official Democratic loyalty test of chairman RonBrown. Casey is pro-life, and so he was gagged for the entire New York celebration of Democratic pluralism.

Finally, in the Great Hall of Cooper Union, the governor was to address the question that the Democratic leadership considers subversive: "Can a liberal be pro-life?"

Tony May, a press aide to Casey, told me: "We were looking forward to speaking in New York. It's an intellectual center, so we figured the level of this discussion would be higher there than we've been used to in Pennsylvania."

As moderator, I started what would have been the discussion by pointing out that this was an evening about free speech -- not only that of the governor of Pennsylvania but also that of anyone in the audience who wanted to challenge him.

The hooting, screaming, pounding and whistle blowing began. Strategically located at both sides of the hall -- disruption by stereo -- a preening array of hooligans made all speech except their own inaudible. They reminded me of the domestic brown shirts breaking up Jewish meetings in my youth, but these were howling soldiers of the left. (There is no difference, of course, between right and left when it comes to silencing the bearers of uncomfortable ideas.)

Among the opponents of any free exchange of ideas were ACT UP and various pro-choice (sic) cadres, among them: WHAM (Women's Health Action Mobilization); and NYU Students for Pro-Choice.

At least 80 percent of the audience wanted to hear Casey and said so, as best they could, by applauding his attempts to get started. But they were no match for the speech muggers.

After several tries, Gov. Casey yielded. "The Democratic Convention suspended the First Amendment," he tried to say, "and tonight you did the same thing." Casey walked off the stage as the shouters congratulated each other.

An ironic obbligato to the evening was the presence of an especially raucous contingent of righteous censors -- a group concerned with the fate of Mumia Abu-Jamal, who is on death row in Pennsylvania. Convicted of killing a policeman, Jamal has exhausted all his direct appeals, and his lawyers are now beginning to try other avenues, which will include a habeas corpus petition.

Jamal's trial -- his lawyers are convinced and I agree -- included egregious violations of due process on the part of the prosecutor and the judge. (Also involved in Jamal's behalf is Amnesty International.)

At Cooper Union, I had intended to ask Gov. Casey a number of constitutional questions concerning Jamal's conviction and sentencing, and I had also expected that some of Jamal's supporters would have raised various specific points with the governor. It would have been the only chance they had to inform Casey directly about the particulars of the case and thereby maybe influence him -- if all else failed -- to grant clemency.

The shouting and whistling prevented a discussion of Jamal's case. A few days after the silencing of Gov. Casey at Cooper Union, Jamal had a visitor in his cell. He is in solitary confinement. Stripped of nearly all privileges, he is only allowed two hours a day outside his small cage and is forbidden radio or television.

But Jamal had heard of what happened at Cooper Union and the fact that the screamers had prevented his case being heard by Gov. Casey. Jamal's visitor told me that Jamal was "surprised, displeased, shocked and saddened" by the self-indulgence of his anti-free-speech supporters.