LONDON -- Former Defense Minister Michael Heseltine challenged Prime Minister Margaret Thatcher yesterday for leadership of Britain's Conservative Party and the country, throwing the entire political scene here into turmoil.
He acted less than 24 hours after Mrs. Thatcher was subjected to a devastating attack in the House of Commons by her former deputy, Sir Geoffrey Howe, over her anti-European attitude.
"I am persuaded that I would have a better chance now, a better prospect now, than Mrs. Thatcher of leading the Conservatives into a fourth election victory, thus avoiding the ultimate calamity of a Labor government," he said.
For the past year the opposition Labor Party has held a double-digit lead in opinion polls over the Tories, and Mrs. Thatcher's own popularity has plummeted as her strident style of leadership, her negative posture toward Europe and her handling of the economy -- now in recession -- have come under increasing criticism.
Her anti-European policies were the catalyst of the crisis but were thought to be unlikely to be the decisive factor in the vote on her future.
The election, to be held Tuesday, will involve the 372 Tory members of Parliament. They are to decide which candidate has the best chance of ensuring their own re-election in the next general election, to be called by June 1992.
They will judge the difference in styles between Mrs. Thatcher's dominating leadership and Mr. Heseltine's inclination to seek consensus, observers said. They also will weigh the varying emphases of the two candidates on policies ranging from the economy to the environment.
They also must decide whether Mrs. Thatcher can now continue to lead the party without inflicting the permanent image of disunity on it.
One Thatcher insider admitted, "Leadership challenges are damaging politically, especially in a country which has so far put so much emphasis on unity in a political party."
Under the voting rules, Mrs. Thatcher, 65, will need 214 votes to win outright and continue her 15 years as Conservative Party leader and her 11 years as prime minister. Mr. Heseltine, 57, said he decided to run after receiving pledges of support from more than 100 MPs.
The campaign will not be conducted openly but will be fought in the parliamentary corridors of power, with each side twisting as many arms as possible.
If neither candidate finished with a 15 percent majority over the other on the first ballot, a second-round vote would be held a week later and other candidates could enter. In a fragmented field, it could take several votes for a winner to emerge.
Foreign Secretary Douglas Hurd, who nominated Mrs. Thatcher for re-election, was careful yesterday not to rule out his own late entry as a candidate.
If Mrs. Thatcher were defeated, it would be the first time this century that a prime minister was thrown out of office by a revolt within his or her own party.
Mrs. Thatcher's supporters expressed confidence that she would win the first ballot but added that she was prepared to fight to the finish.
Norman Tebbit, a former Conservative Party leader and one of her campaign managers, said, "Mrs. Thatcher is a fighter."
He said she had won leadership of the party against male prejudice, had won three general elections, had won the Falklands War and had won British interests in Europe.
One of Mrs. Thatcher's aides said of Mr. Heseltine: "He has made no secret since he was at university that he wanted to be prime minister. His challenge has to be driven by ambition in the first place."
The aide said that the political fight would create a period of uncertainty and would damage the party.