Winston Churchill was forced out - twice. Margaret Thatcher was ousted by her own party. John Major was removed by the electorate.
Tony Blair has other plans.
The prime minister's unprecedented announcement that he will leave office on his own terms has short-circuited ruminations on the embattled Mr. Blair's future and the possible look of a post-Blair Britain. Blair says he intends to fight in the next election expected next May and, if successful, serve a third full term before yielding to a successor, probably around 2009.
Supporters say the plan could free his hands to complete the "Blairite" project of modernizing Britain. But skeptics worry the nimble leader - already dogged by the unpopular war in Iraq and charges that he has neglected domestic reforms - will be reduced to a lame duck as squabbling acolytes maneuver to succeed him.
Tim Allan, who served for four years as Blair's deputy press secretary, says the move neatly demonstrates a deft touch for proactive strategy. "The decision bears all the hallmarks of a Blair strategic decision," says Mr. Allan. "He's very good at working out where he should be positioned in any big argument or debate."
The political debate this year has centered on Blair's future. His popularity has ebbed because of the Iraq war, which met heavy public protest from the start. A heart operation, though conducted successfully on Friday, has triggered questions about his political longevity. Putative successors have long been jostling for position, not least his right-hand man, Gordon Brown.
But Blair's chief strengths through seven years in office have been decisiveness, excellent communication, and political dexterity. Blair has, moreover, a keen sense of history, and knows that British prime ministers do not last forever. "I think it's sensible now to say to people 'frankly, I wouldn't go on and on and on,'" he said, alluding to Margaret Thatcher's fateful boast to "go on and on."
Allan says that the decision could breathe new life into Blair's agenda. The Iraq war has unquestionably deflected attention from the chief mission for which he was first elected in 1997: to modernize public services, schools, hospitals, and transport systems neglected throughout a generation of underinvestment.
"One argument is that your power starts slipping as soon as you say you're going, but it also gives you the freedom of a 'second term presidency' - you're no longer thinking of the short-term tactical thing of how do I keep my job," he says.
But others say setting a limit to his term presents the kind of problems that American presidents face late in their second term, when time is running out. Unlike American leaders, British prime ministers face no term limits. They stay in the job until they are voted out by party or country, or until they quit.
"The [US] phenomenon ... of the lame duck president in [the] last two years of his term doesn't exist here, but this has introduced it," says Paul Whiteley, professor of politics at Essex University.
John Rentoul, political commentator and author of the biography "Tony Blair: Prime Minister," says the danger is that, "Once you set a date for your departure in the British system, then power begins to drain away from you."
The fear is that soon after the next election, which Blair's Labor Party is expected to win, the business of government will be subsumed by a succession struggle. Mr. Brown is the heir apparent, but there is no shortage of potent challengers, including the smooth, telegenic Alan Milburn, the durable foreign secretary Jack Straw, the tough Scot John Reid, and the youthful intellectual David Miliband.
So why not just quit now? Blair says he still has things he wants to achieve. "I've got lots more I want to do," he said in Thursday's televised interview. "I do want the chance to finish the job that was started.... I believe I can still make a real contribution to this country."
His remarks are seen as an effort to put the unpopular Iraq situation firmly behind him and return to the Herculean task of domestic modernization. Above all, Blair does not want to go down as the man who fought controversial wars overseas but shirked key battles at home.
"He'll want to see at least a partial resolution of the situation in Iraq, and proceed further in modernization of public services - there's still some way to go in that," says Wyn Grant, professor of politics at the University of Warwick in central England.
"He needs to win another mandate to expunge the charge that Iraq has destroyed his premiership," says Rentoul. "This is all about securing the reform of public services, because that's the only legacy left to him now."
Achieving that might also enable him to win back the affection of his own public. Though extremely well-regarded in America on account of his staunch and eloquent support for George Bush's war on terror, Tony Blair has watched his popularity at home ebb over the past four years.
The youthful enthusiast who swept to power by appealing to all sections of society has found it impossible to please all of the people all of the time. Certain segments have become disillusioned - by the Iraq war; by rising taxes; by the slow pace of reform; and by perceived hostility toward interest groups such as teachers, public sector workers, and rural dwellers.
"His ambiguities when he came to power allowed him to represent everyone's hopes and no flesh-and-blood politician could keep all those hopes alive," says Rentoul. "The process of the past seven years has been alienating one section of society after another."
By 2009, Tony Blair could be the longest serving prime minister for more than 100 years, longer-lasting even than Thatcher, Churchill, Lloyd George, and other giants of modern British history.
But he will only be 56. So what next? He currently has a 4-year-old son as well as three older children. The international political stage could beckon, but, tellingly, he and his wife Cherie have just bought a 6.5-million-dollar house in central London. Friends guess the future may lie closer to home.
"It wouldn't surprise me if his future plans were not to do with ongoing international politics but were rather more personal and low key," says Allan.
"He's a very driven guy with strong religious beliefs and wants to achieve certain things in his life, but he's not a political obsessive. I don't imagine he'll hang around Westminster any longer than necessary."