Apolitical party has room for only one leader, and those in Ontario politics who refused to accept this fact usually have had their political careers cut brutally short.

This has happened to Michael Bryant, who held several cabinet posts competently in a decade as an MPP and made no secret that he wanted to succeed Dalton McGuinty as premier, and the sooner the better.

Premiers want ministers to be enthusiastic, but not breathing down their necks, and the strained relations between the two have prompted Bryant to leave for a less influential post with the City of Toronto.

Bryant joins other politicians whose careers were cut short because they were over-eager to have the top job. William Davis, premier from 1971 to 1985 and the longest-serving premier of recent years, faced no fewer than three such challenges.

Davis, the establishment choice, won by only 44 of the 1,580 votes cast in a Conservative leadership convention because of an unexpectedly strong run by a little known minister, Allan Lawrence, that showed the party was divided and prompted suggestions they should almost share power.

Davis was cool to this and gave Lawrence a newly-created job developing justice policy that kept him out of the public eye, which is death to a politician, and soon afterward he left and was elected federally, but never came close to the prominence his earlier march to the threshold of being premier had promised.

Davis also felt threatened by Bert Lawrence (no relation), another losing candidate for leader who provided some of the brightest ideas, but found an excuse to drop him from cabinet when he used a government plane to take his wife and two children to Cuba without clearing it with the premier.

Lawrence explained that he was trying to promote trade, but it appeared to be a misuse of public funds and a second pretender to the throne quit provincial politics.

After the Davis-led Conservatives won only minority governments in two straight elections, the most serious attempt to replace him was launched by Darcy McKeough, another whom Davis had defeated, who had built up a following as an innovative and powerful treasurer.

When Davis made it clear he was in for the long haul and had no intention of quitting as premier, McKeough joined the ranks of the disappointed and left, and the patient Davis hung in and in 1981 even won back the Conservatives' cherished majority.

The Liberals had a similar episode in opposition in the 1960s, after they narrowly chose Andrew Thompson, a former aide to federal leader Lester Pearson, as leader with a push from the party's federal wing, over an unusual outsider, Charles Templeton, an evangelist preacher turned newspaper editor and TV personality.

Templeton hoped for a worthwhile role in the party, but its comfortably entrenched MPPs feared a newcomer telling them what to do and froze him out.

When Thompson resigned because of sickness and faltering leadership two years later, the party begged Templeton to take over, but he had had enough of deceitful politicians and refused.

Ambitious politicians have forced out leaders twice in recent decades. Conservative premier Frank Miller lost the party's majority and then government in 1985, when the Liberals and New Democrats forced him out, but tried to stay as opposition leader.

Larry Grossman undermined him with the cry that the party needed a younger and fresher face, only to lose the next election by an even bigger margin.

Stephen Lewis as a young, oratorically inspiring New Democrat MPP in 1970 collected overwhelming support behind the scenes for himself as leader and presented it quietly to the long-serving leader, Donald C. MacDonald.

MacDonald accepted he would have difficulty holding on and stepped down, but not without a fight, because he supported another candidate in the leadership race that Lewis won.

Those who have managed to push out leaders usually have had a strong case for it and there is none now against McGuinty.