Clark's resignation throws Canada into political upheaval

Canada's national political agenda has been turned upside down by a single, divisive act by the major opposition party, the Progressive Conservatives. The party's decision last month to throw open their leadership has greatly clouded the outlook for Canada's future choices for prime minister.

The question has exceptional importance because Prime Minister Pierre Trudeau is expected to resign soon, with no clear successor established to take over his party.

Much of the uncertainty arose out of former Conservative Prime Minister Joe Clark's move last week to relinquish the top post in his party and call for a leadership contest. His decision followed a Progressive Conservative convention where Mr. Clark unexpectedly failed to win an acceptable margin of approval from delegates in a confidence vote.

Canadians are flabbergasted that Mr. Clark, after seven years as party leader and now out in front of Mr. Trudeau in the opinion polls, could be publicly repudiated by his party.

''You can bet that whatever the Tories (Conservatives) do from here on, it will be that which is most damaging to the party,'' remarked an angry Conservative who held a senior post in Mr. Clark's six-month government in 1979.

The situation has grown more confusing because prominent contenders for Clark's post have declined to step into the fray, leaving Clark the only declared candidate.

In the resulting frenzy of speculation, the major beneficiary has been Peter Lougheed, the premier of the western oil-producing province of Alberta. Mr. Lougheed, who almost single-handedly brought the Conservatives to power in his province, has for the past week been besieged by an unprecedented movement to prod him onto the national political stage.

In telephone calls, letters, hand-delivered requests, and petitions, thousands of fellow western Canadians have appealed to Mr. Lougheed to try to become the Progressive Conservatives' standard-bearer. This pressure has arisen in spite of Mr. Lougheed's repeated disavowals of any national political aspirations.

Many Conservatives seem unwilling to accept that answer. They feel the nation is ready for Mr. Lougheed's right-wing philosophy and that his candidacy is essential if the Liberals, who have been in power most of this century, are to be ousted.

Mr. Lougheed, recently reelected in Alberta, has said he owes it to the province to stay in his current position. Also, he wants to avoid a nasty fight with Clark, also an Albertan.

Another favored contender for Clark's job is Bill Davis, premier of Ontario for 11 years, the country's most important industrial province. But he has so far declined to challenge his party's battered leader. The same goes for Brian Mulroney, a Quebec businessman and prominent Conservative.

The key question is whether the Progressive Conservatives, currently far ahead of Trudeau's Liberals in public-opinion polls, have by throwing open the leadership issue hindered their chances of winning the next election. Some say the nationally televised spectacle of a party cutting down its leader may have caused irreparable damage. Others say it was a necessary part of finding someone who can unify the party.

With their main opponents in disarray, Liberals have been given a tremendous chance to rebuild their own party, which under Trudeau since 1968 has been all but wiped out electorally in the western provinces.

Because the Conservatives will require six months to hold a leadership convention, the Liberals can now take their time in setting in motion the process of picking a new leader of their own. A front-runner is Toronto lawyer John Turner, a former Liberal finance minister. But Mr. Turner has been out of politics for seven years after a split over economic policy with Trudeau and may not enjoy widespread support within the party.

Another possibility is Donald MacDonald, also a former Cabinet minister who has recently been given the high-profile task of heading a special commission on the economy. But his reputation may be tarnished by the furor over the level of his pay - more than $600 a day for the three-year study of Canada's suffering economy.