Ontario holds the key, and the most voters, in Canada's elections

Ontario is key to the outcome of the Canadian federal election on Sept. 4. The reason is simple - Ontario has more people and more voters than any other province in the country.

With almost 9 million people it has more than one-third of Canada's population. And the voting habits here swing with every election.

The Progressive Conservatives seem set to win the federal election: Polls show them well in the lead. They have almost caught the Liberals in Quebec, where the ruling party holds 74 of the 75 seats. A swing to the Tories in Quebec would give Brian Mulroney, the Tories' new leader, a big majority in the House of Commons.

But he won't get anywhere without Ontario and its 95 seats.

The people of Ontario are a bit of a bellwether. You can't help but be if you're that big. In the 12 federal elections since 1949, Ontario has gone with the winner in every contest but two.

Take the last two elections. In 1979 the Conservatives under Joe Clark made big gains in Ontario, picking up 29 seats they hadn't had before. They won the election, though with a minority government.

The Tories were defeated on a budget measure and had to call another election in February 1980. The Liberals under Pierre Trudeau won 19 seats back. With that they won the election - and a majority government.

Going into this election, the Liberals held 52 seats in Ontario, the Conservatives 38, and the New Democratic Party (NDP) 5. But a recent poll by the Canadian Broadcasting Corporation shows those numbers could be topsy-turvy on election night. The poll, released 15 days before the election, shows the Tories have 48 percent of the support in Ontario, the Liberals 32 percent, and the NDP 20 percent. Those numbers could mean upsets on election night.

The NDP might hold on to its seats. It might even gain some in the province, if it can marshal its strength in the right districts. But the once-mighty Liberals look to be in trouble.

With the party tallying only 32 percent in the polls, some big Liberal guns could be collecting parliamentary pensions sooner than expected. Ontario has 12 ministers in the federal Cabinet and a lot of them are in tight races.

John Roberts, the minister of employment and a former candidate for the Liberal leadership, is battling the Conservatives in his rich Toronto district. His opponent is Barbara McDougall, a former executive with a stock brokerage house. Other Cabinet ministers in trouble include David Smith (small business), Judy Erola (consumer affairs), and Ralph Ferguson (agriculture).

The swing to the Tories is especially noticeable in Toronto, which is known locally as 'Metro.''

It has been made possible by William Davis, the Conservative premier of Ontario who has thrown his support behind Mulroney and given him the use of one of the finest political organizations in Canada.

The Conservatives have been in power in Ontario's provincial legislature for more than 40 years. They know how to win elections. Last time Mr. Davis and his friends all but ignored Mr. Clark, who had ideas about energy prices which Davis didn't like - and Clark lost.

Mulroney has ruffled Davis's feathers only slightly by suggesting that Ontario be made an officially bilingual province. The move gained the wily Mulroney some support in French-speaking Quebec without costing him much in all-important Ontario.