In ancient times, when the Caesars won a big war, they used to chain their most prominent captives to chariots and drag them through the streets of Rome for the population to jeer at. Senate Republicans are doing something very like that to Bill Clinton in the wake of his massive defeat on the Comprehensive Test Ban Treaty.

They are not content to have beaten him on a cosmic issue. They want to humiliate him into the ground. Having failed to remove him from office in his impeachment trial last February, they are having another crack at it legislatively. To their contempt for him, they add their contempt for his office. He begged them to put off consideration of the treaty to avert the shameful sight of Uncle Sam abdicating moral leadership on non-proliferation.

Both sides toyed for a while with the idea of requiring him to limit his 14 remaining months in office to areas to be defined by the Senate. He was to promise in writing that he would not bring up the issue again while he is in the White House.

Majority Leader Trent Lott (Miss.) said with a straight face in the middle of the feverish politicking going on in the back rooms and corridors, "we must keep it out of politics." It was, as Sen. Joe Lieberman (D-Conn.) said on the floor, "unusual and unsettling" for the Senate to turn down a president's request to have an international treaty pulled back. But the Republicans were, in nuclear parlance, "making the rubble bounce." They always go too far.

Last week, they had demeaned themselves by rejecting a judicial nominee, a black Missouri judge named Ronnie White. Both Missouri members had requested it, one strictly for campaign purposes. But that was a club matter. This was a question for the world. Lott made it a matter of party loyalty. No measure, it seems, is too large or too small to be petty about.

In the world outside, the Pakistan military staged a coup in the newly nuclear state. To other minds it might have seemed an argument for pushing ahead with a test ban treaty which, whatever its flaws, could have an inhibiting effect on nationalistic zealots seeking to take the next step in weapons development. India's hostile neighbor had signaled its willingness to sign the treaty. Lott could see no relevance.

Lott, according to national security adviser Sandy Berger, turned the Senate's "advise and consent" function to "hit and run." After two years of inaction, he suddenly scheduled a vote, with only one day of hearings. He was reminded that if Clinton is a captive of the Senate, he is a captive of his right wing. He tried to shield his flock from the fallout of a vote rejecting the treaty. He worked with Democratic leader Tom Daschle (S.D.) to fashion an agreement that would pull the treaty on receipt of promises that Clinton would not try again except under "unforeseen circumstances."

That phrase did not please Lott's implacables. Sens. Jon Kyl (R-Ariz.) and Jesse Helms (R-N.C.) tracked him down in his office and raged at him for even considering any clemency for Clinton. They wanted to vote the treaty down for all the world to see. The "fragile and tentative" agreement collapsed.

The recriminations began with the laments. Congress complains that the president did not preach and press early enough. He put on panels of clergymen and soldiers who favored the treaty at the last minute. He invited 10 swing senators for a sales dinner. The White House wishes that the Democrats had not accepted Lott's ultimatum to put the vote on a fast track. But the 82 percent of the American people who declared themselves for the treaty hardly knew the process had begun before it was over.

The long hearings that other treaties have been subjected to were needed to make the converts in the Senate who would make the difference. The Europeans did their best, Tony Blair, Gerhard Schroeder and Jacques Chirac taking the extraordinary step of submitting a New York Times op-ed plea for passage. European papers carried page one stories every day about the madness in the Senate.

Usually, our politicians claim how great the country is. The Congress wants to present Uncle Sam as a fearful giant sitting on the sidelines on nuclear disarmament: We don't test ourselves but we don't care what others do. We're a deadbeat at the U.N., and won't pay the almost billion dollars in dues that we owe. In the Republican Party, the moderates, the internationalists, the arms controllers have been routed by bullies whose foreign policy is a bumper sticker: "We're number one."

They are running the show. The U.N. High Commissioner for Human Rights, Mary Robinson, came to town last week and suggested gently that we might not want to substitute "raw force for moral authority." That is however, just what the Republicans have in mind.