LONDON, NOV. 12 -- For Michael Heseltine, a fabulously wealthy, endlessly ambitious politician, the moment of truth appears to be at hand.

After four ambiguous years of on-again, off-again attempts to succeed Margaret Thatcher as prime minister and Conservative Party leader, Heseltine has now just three days left to decide if he will cast the die. Interest in his intentions has set off a frenzy of gossip, innuendo and character assassination that illustrates just how deeply divided and demoralized the ruling party has become.

"The country needs to know whether Mrs. Thatcher does or does not retain sufficient party support to remain a strong prime minister," The Times of London commented today. "If she does not, she must go. . . .If Mr. Heseltine fails to throw his cap into the ring, he will thoroughly deserve to have it stuffed down his throat."

Ever since he stormed out of her cabinet more than four years ago in a dispute over British involvement in Europe, Heseltine has been grooming himself American-style on the chicken-and-peas circuit to succeed her. It has been a delicate high-wire act -- honoring the unspoken rules of Tory decorum, he has refused to attack her outright, supporting her government while making it unmistakably clear that he wants her job.

Heseltine, whose long, golden hair gives him a theatrical look appropriate for this political drama, has seemed unable to make up his mind about taking on Thatcher. After the protest resignation earlier this month of Geoffrey Howe, Thatcher's deputy prime minister, Heseltine insisted he would not run. Then he released a letter highly critical of Thatcher, suggesting to supporters he had changed his mind. When that prompted criticism that he was firing away at her from a safe distance, he reiterated his non-candidacy.

Then came a pair of by-election defeats for Conservatives that were seen of an indication of Thatcher's increasing weakness. As Heseltine came under intense pressure to confront Thatcher head-on in party caucus balloting to be held in two weeks, his lieutenants feverishly canvassed the House of Commons for votes. He must declare by Thursday whether he intends to oppose Thatcher in the caucus vote.

When asked if he will enter the contest, Heseltine simply says, "No comment."

The opposition Labor Party's continued resurgence in opinion polls, Howe's resignation and the Conservatives' by-election drubbings have all produced a new round of anxiety among those Tory lawmakers who could be swept from their marginal seats in the next general election.

Tory politics may be practiced with an elegant accent, but it is not always a pretty sight, and in recent days the long knives have been out for anyone who dares talk treason. Heseltine, 57, has been described by Thatcher's backers in politics and the press as a brainless nitwit and backstabbing charlatan.

"I am very fond of Michael, but he has absolutely no judgment," said Nicholas Fairbairn, a Thatcher loyalist who did not sound very fond of Michael. "We are talking about one of the greatest political leaders the West has ever known, and we say to ourselves, 'We want to change her for junk.' "

One Tory lawmaker who spoke up for a challenge to Thatcher, Tony Marlow, found both his love life and his haberdashery savaged by the Daily Express, a tabloid known for its intense loyalty to Downing Street. The Express disclosed that Marlow had nine children -- five by his wife, four by a mistress. Worse, perhaps, it reported he often wears white shoes and a black blazer with red and orange stripes to the House of Commons. Marlow refused to comment on either report, the paper said.

Thatcher's supporters, notably Defense Minister Tom King, have even played the Persian Gulf crisis card, suggesting that any leadership challenge at this time could demoralize the 9,000 combat troops that Britain has dispatched to Saudi Arabia.

Thatcher has also been embarrassed at times. After Heseltine released a letter criticizing Thatcher, the Conservative Party's central office dispatched an operative to his legislative district to persuade local leaders to endorse the government. They did so in a mild letter that central office news managers then fed to the press as "a rebuke" to Heseltine. But the locals accused the central party of "dirty tricks" and rallied to Heseltine's cause.

Then someone overheard and reported a car-phone remark that Richard Needham, a junior minister for Northern Ireland, made to his wife. "I wish that cow would resign," he told her -- an apparent reference to Thatcher that found its way onto the front pages of several London papers.

Heseltine's lieutenants have said he would much prefer that a stalking horse such as Howe take on Thatcher in an opening round of the party caucus. If Thatcher were to stumble badly in an early vote, their reasoning goes, she might stand aside, leaving any and all challengers -- including Heseltine -- to jump into subsequent rounds. Howe plans to give a speech in Parliament later this week delineating his differences with the prime minister, but few expect him to challenge her outright.

Thatcher, who is 65, shows no signs of ducking a fight. "I intend to stay in charge for years to come," she told a luncheon of senior Tories last week.

Which leaves it up to Heseltine, whose brand of "caring conservatism" has been described as "Thatcher plus Bush -- a kinder, gentler Thatcherism." Some analysts have predicted that a run now would be political suicide. Others contend that if he does not run after all the canvassing, he will look weak and indecisive, and his chances will permanently fade.