PARIS. — THE ERUPTION of revolution inside Britain's Conservative Party resulted from what Margaret Thatcher was, rather more than from what she had done. What she had done created the political condition in which revolution became possible. The implacable fact was that the Tory Party appeared likely to lose the next general election had Mrs. Thatcher remained its leader.
For months now, the polls have indicated a Labor Party lead. They have indicated that if Michael Heseltine were to lead the party into a new election the Conservatives probably would win.
Whether such forecasts would actually have been borne out in election-day behavior is open to question. Nonetheless, the signs of Tory defeat were enough to have seriously put the wind up among those Tory members of Parliament slated to lose if she had lost. The Conservative Party is not famous for loyalty when loyalty implies defeat.
Europe was the issue which divided her from her challenger, Mr. Heseltine, and other major figures in the party. But what cost her her popularity was current difficulty in the economy with high-interest rates and high inflation, and above all the so-called poll-tax, or Community Charge. This is a new local government tax on individuals, replacing property tax, which has proved wildly unpopular.
It was introduced because the prime minister wished to punish high-spending, Labor-controlled local authorities. She wanted all the voters, not just property-owners, to suffer from Labor profligacy. What she instead did was make the new taxpayers furious with her.
There is also a widely held belief in Britain that the National Health Service, and the country's schools and social services, have deteriorated as a consequence of her policies. Her supporters insist that not only absolute but relative government spending on these services is higher than it was under the last Labor government, but this has not changed opinions.
Her insistence on privatizing not only elements in the health service but Britain's water, electricity and other public services, the deterioration of railways and of the transportation infrastructure, and her political program for remaking Britain's broadcasting system to favor commercial broadcasters, have contributed to a sense many Britons have of upsetting and unnecessary change, usually for the worse.
But the challenge to her rule was not a voter rebellion. It was a repudiation by fellow-members of the Tory parliamentary party. This resulted from the way she treated cabinet colleagues. For a long time she has had the reputation of haranguing and humiliating them in private, while undermining or tarnishing the public reputation of any colleague who disagreed with her.
Cabinet government in Britain is entirely different from presidential government in the United States. The members of a British cabinet are supposed to possess power in their own right, and government policy, which the prime minister articulates, is supposed to represent their collective judgment.
Mrs. Thatcher had publicly reversed or contradicted positions painstakingly worked out and agreed to in cabinet. Thus one after another of the major Tory politicians holding cabinet office have gone -- pushed out, or quitting in anger (as Michael Heseltine, once her minister of Defense did in 1986).
Not a single minister survives from her first cabinet. All who serve today owe their office to her favor. This means that cabinet opinion has become her opinion.
Policy toward Europe -- a place, according to her former deputy prime minister, which she believes ''positively teeming with ill-intentioned people'' -- provided the occasion for this revolt. Her intemperate behavior at the recent Rome summit of the Common Market governments dismayed her colleagues.
Earlier she had humiliated her latest chancellor of the Exchequer, who after much discussion within the government had proposed creation of a so-called ''hard Ecu'' -- a new European currency parallel to the national currencies.
This was supposed to be Britain's answer to the current plan for European monetary union. Mrs. Thatcher remarked to the press that she couldn't think anyone would actually want to use a hard Ecu, leaving the chancellor in a preposterous position.
This practice finally had exploded on her. Sir Geoffrey Howe was Mrs. Thatcher's first chancellor of the Exchequer. He is an earnest, if nondescript, senior Tory, once described by a leading Labor Party figure (Denis Healey) as resembling a dead sheep. (Lady Howe subsequently said: ''Beware the wolf in dead sheep's clothing,'' a warning Mrs. Thatcher should have taken seriously.)