WASHINGTON—Politicians and boxers share a common trait: They never want to quit. The refusal of boxing champions to retire probably stems from an imperial complex. You don’t renounce supremacy conquered through force until a greater force overpowers you. Politicians cling to office because they see service to the state as a lifetime profession—the profession of power—rather than a temporary custodianship. A politician does not cease to be a politician just as an architect does not cease to be an architect.

The premise has exceptions, but Tony Blair is not one of them. He wanted to go on forever. When the whiff of party rebellion was in the air, he made some vague commitment to leave a few years later but nuanced it even further when calm was restored. A few days ago, he met his Waterloo. In an interview, he seemed to toy with the idea of staying on. His party exploded. Gordon Brown, the chancellor of the exchequer and prime minister-in-waiting for the last nine years, moved his pawns against his boss. Blair, humiliated by the resignation of junior ministers and the mutterings of some of his parliamentary backbenchers, conceded. He has just announced—formally, this time—his departure before next summer.

Enoch Powell, a controversial British conservative, famously remarked that all political careers end in failure. Blair’s career had been a success by most accounts: After transforming a fossilized Labor Party that people associated with the “Winter of Discontent”—a time of economic and social disaster in the 1970s—into a formidable political machine, he went on to obtain three consecutive victories. He got rid of the sleaze that had dominated the last Conservative government under John Major but preserved much of Margaret Thatcher’s legacy. The economy did well, experiencing the highest rate of per capita growth among the G-7 nations in the last decade. The opposition Tories seemed lost forever. People even spoke of the Liberal Democrats becoming the second party in British politics.

But three things got in Blair’s way. He decided to become almost a Cabinet secretary in President Bush’s government rather than a partner in the tradition of the Anglo-American “special relationship.” He also decided that the reform of the welfare state consisted of pouring money into the bottomless pit. And, finally, he failed to transform the culture of the party he had so ably led out of the wilderness in 1997.

Becoming so cozy with Bush meant that he would pay the price of failure if U.S. foreign policy failed, and gain none of the credit if it succeeded. Why? Mainly because defeating Islamic terrorism and liberalizing the Middle East through force—Bush’s goals—were not achievable in the short term since many of the variables were not under the control even of a superpower.

Failing to reform the welfare state—a creation of Labor Prime Minister Clement Attlee in the 1940s—meant that sooner or later Blair would find out that no matter how much money you spend on Britain’s socialized services, it will never be enough to serve people’s needs appropriately. Consequently, his second great promise to the British electorate (the first being that he would not wreck the economy) went unfulfilled.

Last but not least, Blair’s party was never as “New Labor” as Blair himself, just as Thatcher’s Conservatives were never as “Thatcherite” as the Iron Lady. In both cases, loyalty was conditional on the perception of success. In the imagination of Labor MPs who are at heart more Fabian than “Blairite,” the combination of frustration in foreign policy and stagnation regarding social services was enough to offset economic success. So they unsheathed the dagger—that time-honored British political tradition.

Belatedly, Blair offered to introduce choice and diversity in Britain’s social services. He made new overtures to the moderate Muslim community. He cut defense spending. These were the signs of a desperate man clinging to power when power started to filter through his fingers like sand.

I met Blair in 1998. “You are not exactly a socialist, you are not exactly a conservative, you are not exactly a liberal,” I suggested. “So who exactly are you, Prime Minister?” He paused and replied, “I am a man of my time. ” He seemed to be implying that the times had abolished those distinctions. They had actually messed them all up. Blair is the son of that confusion and his party has just served him notice that it wants some clarity.