Amid signs that he has failed to overtake the Conservatives, Prime Minister Pierre Trudeau wound up his campaign last night with an emotional appeal for national unity, which he said was "the great issue" in Tuesday's parliamentary elections.

The vote, he said, is "about the kind of Canada we want to build, about the path we want to follow, about the gaps we want to close between the East and the West, the French and the English and the Canadians of many origins."

Quoting from the Gospel of St. John to "love one another" the 59-year-old Liberal Party leader told paritsan crowds in southern Ontario: "I beseech you to keep the aspect of the campaign in mind, the aspect of how do we better share in this great country of ours."

A late Liberal surge in crucial Ontario Province appeared today to have cut somewhat an earlier Conservative lead and there is a general agreement among political writers and pollsters that neither party is likely to win a clear majority of the new Parliament's 282 seats. In the previous 264-seat Parliament, the Liberals held 141 seats and the Consevatives 95, with other parties holding the rest.

Most expeccts predict however that barring some last-minute shifts, Conservative leader Joe Clark seems headed for victory by a narrow margin.

The likelihood of a minority government - either Liberal or Conservative - would leave the balance of power in the hands of Edward Broadbent, leader of the socialist New Democratic Party. While Trudeau, Clark and Broadbent are in agreement on foreign policy, Broadbent's main domestic concern has been a demand for Canadian control and exploitation of resources. Should he emerge as power broker, the major parties would have to make policy concessions that could affect Canadian mining and manufacturing, two-thirds of it controlled by U.S. firms.

the election may have a major impact on the future of the 112-year-old federation, as the new prime minister deals with the issue of French-speaking Quebec and its possible decision to become sovereign.

The Gallup poll published Saturday gave both Conservatives and Liberals 37.5 percent of the decided vote, the surging New Democrats 19 percent and other parties 6 percent. Eleven percent of those questioned stated no preference.

A CTV television poll published today showed the two main parties even at 40 percent with the New Democrats polling 17 percent. The poll showed the undecided vote at 19 percent.

The closeness of the popular vote, according to pollster Peter Regenstreif, would not be reflected in the number of parliamentary seats because of apportionment formulas. He gives Clark a solid lead in parliamentary seats.

Clark, 39, could end up winning a few more seats than Trudeau's Liberals but still not become prime minister.

Trudeau, who after 11 years in office has built an impressive record of political survival, has made it known that he may try to stay in power even if he lost by up to 10 seats. In that case Trudeau would need Broadbent's support.

Such a maneuver by Trudeau could set off a constitutional crisis here despite the precedent set by prime minister MacKenzie King, who was narrowly defeated in the 1925 elections yet clung to power for several months with third-party support.

In view of Trudeau's preoccupation with national unity and his contempt for Clark, political observers here predict that the prime minister is likely to follow King's example.

National unity, ror the long unresolved question of French-speaking Quebec's status within Canada, has acquired critical urgency now that voters in Quebec will be called on to vote whether they want to be sovereign. The separatist Quebec government is expected to hold a referendum, probably in the fall.

Trudeau, who is from Quebec, has insisted that he can provide the type of strong leadership that would prevent Quebec's secession.

National unity has not been a burning campaign issue but it is a subliminal one. Therefore Trudeau has made the question of leadership the main issue of the election campaign, charging that Clark is a weak and indecisive youth who "doesn't know his razzamatazz from a hole in the ground."

Trudeau's aggressively personal attack sought to portray Clark as a "head waiter" parceling out the country to the provinces including Quebec.

The Conservatives have responded with tough television ads. One, for instance, shows Trudeau in the dark being pronounced guilty of crimes against the Canadian economy, to the sound of a cell door clanging shut.

The outcome of Tuesday's vote will be affected by several factors whose impact is difficult to assess.

One id the surge of Liberal Fortunes during the past few days in Ontario, where one-third of Canada's 23 Million people live. Ontario elects 95 of the Parliament's 282 seats.

A second imponderable is the surging popularity of the New Democrats, the only party to pick up strength in the polls - from 16 to 19 points in the last two weeks.

The size of the turnout could affect regional contests. There are roughly 15 million eligible voters.

Trudeau's Liberals are expected to win 60 to 65 of the total 75 seats in Quebec, mainly because the prime minister is a French Canadian. Clark's Conservatives are expected to get 60 to 65 of the total 77 seats in English western Canada (Manitoba, Saskatchewan, Alberta and British Columbia).

The four small maritime provinces (New Brunswick, Nova Scotia, Newfoundland and Prince Edward Island) elect 32 seats. Conservatives expect to win more than half of them.

This leaves Ontario, its affluent middle class soured on Trudeau but still uncertain about Clark, whose tax easement proposals they found attractive. To form a minority government either Trudeau or Clark would need about 50 of Ontario's 95 seats. A majorityu would require about 65 seats.

The daily Globe and Mail of Toronto predicted that the Conservatives may be better positioned to achieve at least their minimum goal because of their strength in the populous southwestern part of the province.

It was in that part of Ontario that Trudeau ended his campaign while Clark was resting in his native province of Alberta. CAPTION: Map, Canadian parliamentary makeup after recent elections, and when last Parliament was dissolved. By Dave Cook - The Washington Post; Picture 1, Pierre Trudeau; Picture 2, Joe Clark; Picture 3, Ed Broadbent