He’s only secure as the next election. Section 4 of the Canadian Charter of Rights and Freedoms requires that there be elections to the House of Commons at least once every 5 years. In practice, the Government dissolves Parliament earlier, usually around the 4 year mark. Since our last federal election was in the spring of 1997, there’s already speculation whether the election will be called for the fall of this year, or the spring of 2001.
At the election, if Mr. Chrétien wants to stay as PM, he must run in a constituency and be personally re-elected to the Commons. As well, his party must obtain sufficient seats to maintain control of the Commons, either by an absolute majority of the seats, or a large enough number that it can form a government with the support of another party. (Note that you won’t find either of these two requirements written down in the Constitution. In fact, you won’t even find any definition of the office of the Prime Minister. These principles are all parts of the unwritten constitutional conventions that we inherited from the U.K.)
There are no term limits on holding the office of Prime Minister, nor for being a member of the House of Commons. The issue doesn’t arise, because in Canada you can’t split your vote the way you can in the U.S. (e.g. vote democrat in the presidential elections, republican in the congressional elections.)
You only have one vote, for your local M.P. If you like what the government’s been doing, you might vote for the candidate of that party. If you don’t, you vote for the candidate of some other party. (There are currently 5 parties represented in the Commons: Liberals (in government), Canadian Alliance (official opposition), Bloc Québécois, Progressive Conservative and New Democratic Party.)
This means that there are no “safe seats” in the way there are in the U.S. A very popular local M.P. may get voted out because most of the voters in that riding decide to vote for another party. Usually, in every election, several Cabinet ministers, the big mucky-mucks of the party, go down to defeat in their own riding (the equivalent of Newt, the House Majority leader, or the chairs of the major Congressional committees losing their seats). On rare occasions, even the Prime Minister loses his own seat, even though the party may return a majority. The last time that happened, to Prime Minister Mackenzie King, another Liberal M.P. resigned his seat and King ran in it. He was elected in that riding.
Overall, the electoral system means that we just don’t have lots of long-serving M.P.s like you do in Congress, and so the issue of term limits doesn’t arise. (Mr. Chrétien is a bit of an exception to this average, having been in Parliament for most of the last 35 years, but there are not many others like him.)
One other point: although Prime Ministers Turner and Campbell were not great successes when they took over the job, that is a relatively recent phenomenon. Prime Minister St. Laurent took over from King in 1947, and won two elections. Prime Minister Trudeau took over from Prime Minister Pearson in 1968, and won the next 3 elections (admittedly, 1972 was a squeaker). He stayed in office for 11 years after taking over, and then 4 more years after the Clark blip in '79.