Conservative opposition leader Joe Clark cleared a major obstacle of his campaign last night by standing his ground against Prime Minister Pierre Trudeau in a nationally televised debate.

In what could be likened to the first match between Muhammad Ali and Leon Spinks, the master debater Trudeau had been expected to knock down his youthful challenger politically by demonstrating to an estimated 7 million Canadian viewers that the two did not belong in the same ring.

In the last rounds of their 30-minute bout, Trudeau opened up on Clark with everything he had. He mocked his language - "let's have a degree of specificity here" - and hectored Clark, retorting disdainfully "Oh, Joe" when Clark sought to respond.

But just when Clark appeared confused and laughed nervously, Trudeau let up the attack, veered off in a different direction and ended on a weak note.

Clark withstood Trudeau's baleful stares, recovered successfully and finished with an effective summation.

Both camps claimed victory. Non-Canadian observers saw it as a draw. Canadian political commentators sugguested that it was a defeat on points for Clark but a very narrow one that amounted to a political victory for the 39-year-old Conservative leader.

Since Clark had not been expected to outclass Trudeau as a performer, Trudeau had to win a decisive victory to boost his party's sagging fortunes a week before the May 22 elections.

But Clark got in a few jabs of his own, telling the aggressive Trudeau to "have faith that people other than you care about this country." Clark accused Trudeau of being power-hungry and described his decade in office as "years of turmoil."

The third man in the debate, Edward Broadbent of the socialist New Democratic Party, scored both against Trudeau and Clark in the individual head-to-head encounters.

While Trudeau was responding to Clark's charges by saying that the Conservative leader would let provincial premiers run the federal government, Broadbent reeled off statistics and brought to the debate the hard-edged reality of unemployment and inflation and cited issues of energy and resources.

The socialist leader - who had little to lose and the most to gain in the debate - came across as a sincere if pugnacious ex-economics professor and his performance was expected to help his party's fortunes.

Both Trudeau and Broadbent went aggressively after Clark. The Trudeau-Broadbent encounter, though, turned into an exchange so friendly that the prime minister was prefacing his statement with a genial "Ed."

By hectoring Clark, Trudeau and Broadbent may have turned off as many viewers as they engaged. They left an impression that Broadbent may support a minority Trudeau government should the Conservatives come in first but fail to get a majority next Tuesday.

Last night's debate, which was far more concrete and enlightening than the 1976 presidential debates in the United States, produced no surprises and was not thought likely to change the committed votes.

But it could have an impact on those who wondered about Clark's capabilities. The Conservative leader demonstrated that he has enouhg stamina and ability to tangle with the best and most experience debator in Canadian politics. CAPTION: Picture, Prime Minister Trudeau, New Democrat Edward Broadbent and Conservative Joe Clark spar before televised debate. Canadian Press via AP