Mr Mulroney will be stepping down after nine years as the head of a government that has been on a roller-coaster ride through public opinion since it was first elected in September 1984 with the largest majority in the history of the Canadian parliament.
Although he brought his party to power and kept it there through a second election by building support in Quebec, he failed twice to reform the Canadian constitution to enhance Quebec's status within the confederation, a move designed to thwart the growth of separatist support there.
Ever since the proposed constitutional changes were defeated in a national referendum in October, Mr Mulroney has kept his party and the public guessing about his intentions. At a key meeting of his party three weeks ago, he indicated he was going to lead the Conservatives into the next election, even though his party is still below 20 per cent in the polls.
In his resignation statement yesterday, Mr Mulroney said he had taken the necessary steps to put his party in a 'fighting position' for the next election and noted the polls had begun to improve marginally. But he also admitted it was time for the kind of change 'that only new leadership can bring'.
Mr Mulroney has already made history by leading his party to two majority victories in a row, something that eluded all his Conservative predecessors this century. Now, he said, he wants to be the first Conservative leader to turn over his party to a successor while the party is still in power.
That claim was an admission he was not confident he could win the coming election. Under Mr Mulroney the government embraced many unpopular policies, including a free-trade agreement with the United States and tax reform that imposed a value-added tax for the first time.
But the Mulroney cabinet was also depleted by several big political scandals, and the Prime Minister's personal popularity had reached the lowest point (9 per cent) since the Gallup organisation began measuring public opinion in Canada after the Second World War.
Canada's traditional three-party system had also begun to fracture with the creation of the Bloc Quebecois, a party committed to an independent Quebec, and the Reform Party, which was making gains in western Canada. The subsequent splitting of the vote, combined with public hostility towards Mr Mulroney, almost guarantees a Liberal victory in the autumn elections. Even with a new Conservative leader, the Liberals would be in a strong position.
Mr Mulroney did not come under any pressure from his party to resign. Conservative members of the parliament, recognising that he had kept the traditionally divided party unified for the past decade, and that he led them to two victories, were prepared to let him make his own decision. Mr Mulroney said he had been thinking about stepping down for the past two years.
Mr Mulroney's move was foreshadowed last weekend when Joe Clark, a longtime Mulroney rival and more recently his constitutional affairs minister, also announced he would not be running in the election.
Among the names mentioned as possible successors are Kim Campbell, the Defence Minister, who was until recently the justice minister and known for making reforms in the legal structure; Perrin Beatty, the Communications Minister; Barbara McDougall, the External Affairs Minister; and Michael Wilson, the Trade Minister.