Mulroney, back in Canada, may wish he had left someone minding the store

Canada's prime minister, Brian Mulroney, returned to his native land yesterday to trouble, trouble, trouble. The leader of the Progressive Conservative Party had flown to Tokyo hoping to bathe in the glory of the summit and subsequent state visits to China and South Korea. Instead, Canada's news media have been dominated by a series of political blows to his party's fortunes:

On Monday, a senior Cabinet minister, Sinclair Stevens, resigned, beset by conflict-of-interest allegations. He was the fifth Cabinet minister to resign under fire since the Mulroney government took office in September 1984.

Also on Monday, the General Accounting Office of the United States Congress concluded that Michael Deaver, former top aide in the White House, may have violated US laws by lobbying for Canada. The Justice Department is now investigating.

Mr. Deaver, a personal friend of President Reagan and his wife, helped the Canadians in their efforts to obtain US concessions on the issue of acid rain in time for the meeting of Mr. Reagan and Mr. Mulroney last March.

``The fact is, this government is guilty of impropriety,'' charged Lloyd Axworthy, a Liberal member of Parliament from Winnipeg.

On Wednesday, Robert Toupin, a Conservative member of Parliament from a constituency outside Montreal, announced he was quitting the Conservative caucus to sit as an independent. He gave as his reason ``a profound disagreement'' with Tory philosophy and the behavior of some individuals in the Conservative Party.

The shift in no way threatens the Mulroney government. The Conservatives still have 209 seats in the House of Commons, compared to 39 for the Liberal Party, and 30 for the left-leaning New Democratic Party. There are now two independents and two vacancies.

Moreover, Mulroney has at least two years before he would be expected to call another election. Nonetheless, the troubles clearly annoyed him.

``The honeymoon period is definitely over,'' says Robert Jackson, a political science professor at Carleton University here. ``The Conservatives will have to fight for every vote.''

Ramon Hnatyshyn, government House leader, says he doesn't read too much into this week's troubles. ``We have had our ups and downs,'' he says.

The Saskatoon, Saskatchewan, politician noted that it is not uncommon for democratic governments to face a political slump after they have made a number of decisions. He recalls that previous Liberal governments suffered from ministerial resignations and party defections.

But David Collenette, secretary-general of the Liberal Party, noted that in every federal by-election or provincial election since the Conservatives took office in Ottawa, the Conservatives have either lost completely or have seen their voter margins shaved.

The latest national opinion poll shows the Liberals with 41 percent support, the Conservatives 37 percent, and the New Democratic Party 21 percent.

``Canadians haven't really made up their minds on whom to support,'' he says.