Pierre Trudeau, who announced he was quitting politics and was considered washed up only three months ago, staged one of the most remarkable political comebacks in Canadian history today by winning a fourth term as prime minister.

Trudeau, 60, led his Liberal Party to an overwhelming victory over Prime Minister Joe Clark's Conservatives and took an overall majority of Parliament's 282 seats.

The Liberal resurgence reflected a clear repudiation of the 40-year-old Clark's leadership and his economic austerity measures.

With 80 percent of the ballots counted, the Liberals were collecting 49 percent of the popular vote followed by the Progressive Conservatives with 31 percent and the socialist New Democratic Party with 22 percent.

According to official results, the Liberals held 148 seats, the Conservatives 100 and the socialists 33.

Trudeau, in his victory speech here, paid a warm tribute to Clark's "courage and faith." He also said his election success was a mandate to keep Canada united and counter the threat of French-speaking Quebec's secession. Trudeau also hinted broadly that his government would seek a greater involvement in world affairs noting that Canada is geographically situated between these superpowers."

Clark, speaking at his headquarters in Spruce Grove, Alberta, conceded defeat by saying:

"The people of Canada have exercised their democratic choice. We naturally accept the defeat. I extend congratulations to the Liberal Party on the success of their campaign and wish them well in dealing with the very serious problems and very great tensions in this country."

For Trudeau, who served as prime minister for 11 years before he was defeated by Clark, today's victory represents personal vindication as well as a mandate to carry out his policies, which were repudiated by English-speaking Canada in May.

Clark was the youngest prime minister in Canadian history. The defeat could well mark the end of his political career, since he had been blamed by senior Conservative figures for the party's poor showing.

The shift to the Liberals was clear after a campaign that largely focused on Clark's austerity budget, which included an 18 cents a gallon tax increase on gasoline, and on the perceived indecisiveness and weakness of the Conservative leader.

It was the second time in less than nine months that Canadians were called on to pick their leader. Officials estimated that 70 percent of the country's 15 million eligible voters cast their ballots.

The Liberals' winning trend was set early in the evening when the first returns showed that they picked up five additional seats in the Maritime provinces and made strong showings in the crucial province of Ontario.

It was clear from the outset that Ontario -- the country's industrial powerhouse that comands one-third of Parliament's seats, would decide the outcome.

Ontario's swing to Clark in last year's election made his Progressive-Conservative Party the largest in Parliament with 136 seats and brought to an end 16 years of Liberal rule. The Liberals won 116 seats, the New Democrats 27, while the small Quebec-based Social Credit Party won 5.

Yesterday, in a meeting with Conservative candidates in Toronto, Ontario's -- and Canada's -- largest city, Clark held out the hope for victory in today's election. After his speech, however, a 12-year-old boy sang for the prime minister the theme song from the Broadway musical "Annie" that promises that the sun will come out tomorrow and clear away the cobwebs and sorrows of today. Some of the Conservative leaders appeared close to tears.

Clark, who became prime minister before his 40th birthday, is largely responsible for the necessity of today's election, according to government memos published today in the Ottawa Journal.

By failing to predict the strength of the opposition to his budget, Clark's government was brought down Dec. 13, when Liberals joined the New Democrats to reject his austere program, which called for sharp increases in the price of gasoline.

Although counseled by his advisers then to engage in parliamentary maneuvers to prolong the life of his Cabinet until spring, the Conservative leader decided to face an early election, convinced by private polls that he would be reelected. Clark himself made the decision, the newspaper said.

A factor in the decision was Trudeau's earlier announcement that he was quitting politics, which left the Liberals without a leader.

With new elections only two months away, the Liberals had little choice but to call on Trudeau to come back. Canadians suddenly discovered that his career was not over yet.

The eight-week long campaign was in many ways a rerun of their last year's fight, except that the roles seemed reversed. Trudeau was defeated last May after 11 years as prime minister, repudiated by English-speaking Canadians who seemed tired of his combativeness, his arrogance and his policy of dealing with national unity and Quebec separatism.

The awkward and inexperienced Clark emerged as the focus of this year's campaign. The change of voter mood appears to come less from any new enthusiasm for Trudeau than from a disappointment with Clark's image as a weak, ineffectual leader and resentment of economic austerity measures on alcoholic beverages and tobacco.

One underlying factor that has contributed to the change of mood, especially in Ontario is the prevailing perception that Clark's Conservatives, who enjoy overwhelming strength in the resource-rich western provinces, were prepared to sacrifice the interests of Ontario industries by seeking higher energy prices.

The western provinces, particularly Alberta, provide 85 percent of Canada's oil needs and all of its natural gas requirements. While Clark wanted to bring Canadian oil and gas prices closer to the world levels, Trudeau has argued that domestic prices should be kept at lower levels to "maintain and enhance Ontario manufacturers' competitive position in foreign markets, especially in the U.S. market."

Until last week the Liberals have kept Trudeau on a short leash with minimum public exposure, doing all they could to avoid stirring old anti-Trudeau sentiments. Instead, they ridiculed Clark's image and placed him in the focus of public attention.

The Liberal attacks on Clark's policies and broken promises have been detailed and to the point, while their own plans and policies were vague and blurred.