It is happening. The hammer and sickle flaps companionably with the Stars and Stripes on the lampposts of Pennsylvania Avenue across the street from Ronald Reagan's White House.

A white truck lumbers past Lafayette Park, a wooden horse's head protruding from the rear. Its warning: "TROJAN HORSE -- INF Treaty Is Appeasement."

The coming of Mikhail Gorbachev has churned up the national psyche. People like him, hate the system he represents, long for peace, fear the peacemaker. Two hundred thousand people occupied the Mall Sunday, shouting for freedom for Soviet Jewry. It is a family party, with children romping about and several generations picnicking on the cold ground.

"It was a schlep, but worth it," said a young computer executive, who came on a bus from Teaneck, N.J. "Even if Gorbachev pays no attention, Anatoly Shcharansky says the word filters down to the camps and people take heart."

The Soviets know that human rights violations represent the stumbling block to the millenium they propose. Disarmament is the answer to everything. Gorbachev, having learned the difference between propaganda and public relations, deployed 160 spokesmen to prepare his way. Academicians, lawyers, scientists, swarmed over the city, available, affable, on the record. Ask them about anything: warheads, perestroika, human rights, legal reform. They tell of a Human Rights Commission with Andrei Sakharov, patron saint of dissidents, as a consultant. They tell of changes in the criminal code with new grounds for sending people to insane asylums.

After four days of seductive rhetoric, they called it off. A Sunday session on regional conflicts was canceled. Enough glasnost for a while.

For Americans, there was only one question: Can they trust Mikhail Gorbachev? Not for him the wooden overcoats of his predecessors. His suits are made in Rome. He's a salesman. It's a bill of goods, howls the right.

The Soviets were putting out an all-points bulletin. The voices were many, but there was one message: "We've changed. Forget KAL, forget the camps. We are into 'new thinking.' " Said Fedor Burlatsky, an academician in a press club panel, "We are determined to achieve a more efficient, democratic, more humane Soviet society."

A tall, dour man named Vladimir Kudryatsov, director of the Institute of State and Law, is asked why the Soviets use the alibi of possession of state secrets to keep Jews in Russia. All will be well, he suggests, once we agree about arms. "If we can further arms control, the number of secrets we have from each other will be much decreased so it will be less of an issue."

Ronald Reagan, the man who could have been expected to lead the opposition to the Soviet offensive, appeared on the tube saying that enemies of the INF treaty simply couldn't shed their foolish notion that war is inevitable. He was asking them to give up the ogre who had served him and his contemporaries all their lives. With the Soviet menace gone, who will be to blame? His old followers feel the ground shaking under their feet.

It is hard to make a case against the INF treaty, a paltry accord that Gorbachev and Reagan are signing. The Soviets give up four warheads to every one we scrap. Four percent of the nuclear arsenal is involved. But it isn't what's on the paper but what's on Gorbachev's mind about other cuts -- 50 percent in big nukes -- that gives the right the shrieks.

The Madison Hotel is full of people with trenchcoats plainly not made in the U.S.A. It has been taken over by the Gorbachev support troops. An interview with Evgeny Velikhov, the savvy, vice president of the Soviet Academy of Sciences, is interrupted by an enormous, panting police dog to check the room for bombs. Velikhov accompanied Gorbachev to Geneva and Reykjavik; he sees this summit as a peak of hope for a new, rational superpower relationship.

"Quite unfortunate," he sighs of the incident that put the brakes on any idea that the "new thinking" of the briefings has reached all levels of the police state. The sight of bullies roughing up a pitiful protest of refuseniks in Red Square was played on all networks Sunday night, contrasting with the joyful, giant gathering on the Mall.

"On our side, are thinking CIA," says Velikhov. "Your side thinking KGB."

On the bureau is a picture of him with three U.S. Democratic congressmen at Krasnoyarsk, the secret Soviet radar site. It was his idea to show the United States how far the Soviets are willing to go in on-site inspection.

"Is good," says Velikhov, "for KGB to see Americans at a sacred place."

Now Gorbachev is at our sacred places, and hope, no matter what anyone says, attends him.