Not before Tuesday afternoon will we know whether Michael Heseltine has achieved his almost lifelong ambition to lead Britain's Conservative Party and the country; although he may be the front-runner, he isn't assured of the 50 percent plus one that he needs to win, and a third ballot could be dicey. But whatever happens, Heseltine, as the agent of Margaret Thatcher's political demise, has a secure place in Tory party annals. Regicides are well remembered.

Because Mrs. Thatcher was a woman and an outsider in a party that had always been led by insiders, she was as interesting at first for who she was as for what she might do. So it is with Heseltine. First, he has the distinction of having been for many years at the head of the list -- a long one -- of Mrs. Thatcher's political enemies. In the dual role of her implacable enemy and would-be successor, Heseltine came close to bringing her down nearly five years ago when he resigned as defense secretary in the middle of a Cabinet meeting, stalking theatrically into Downing Street -- protected against some bitterly cold January weather only by his Saville Row suiting.

He was reacting to having been overruled in his leader's characteristically highhanded way on a dispute over whether an insolvent helicopter company called Westland should be sold to an American company -- her preference -- or to a consortium of European firms, as Heseltine had urged. The blundering and deceit within the government, especially at No. 10 Downing Street, that followed Heseltine's departure could have brought down Mrs. Thatcher (as she openly feared it would), but she was spared by the ineptitude of her opposition's front bench. The Westland affair was much the worst scandal of the Thatcher era. And close Heseltine watchers saw what struck others as an impetuous resignation as a carefully planned and well-executed act.

Careful long-range planning is among Heseltine's hallmarks. He thinks ahead, they say, not in years but in decades. Julien Critchley, a Tory member of Parliament who was with Heseltine at Oxford, has written that his friend's resolve to become prime minister by the 1990s was pronounced during university days. And Heseltine is said by others who know him to be designing a garden at his country house in Oxfordshire that will enclose many kinds of trees that will not mature until after his death.

Although Heseltine went to a public (i.e. private) school, he might bear some resemblance to the kind of Tory that Mrs. Thatcher tried to foster -- the rich, self-made entrepreneur. Heseltine did become immensely wealthy with a publishing and real estate business. But he never really was "one of us" -- the term chosen by Mrs. Thatcher and the arditi (a term for her fellow revolutionaries) to distinguish themselves from the more orthodox members of their party. Heseltine was -- is -- a mainstream Tory, convinced that the state can and should be a constructive force within a free-market economy. Although like Mrs. Thatcher, he has favored privatizing the public sector, he has trashed many of her pet economic notions. The managed capitalism of Japan and Germany is Heseltine's model, whereas Mrs. Thatcher arrived determined to strip away government's involvement with the private sector.

Also Heseltine could never have been "one of us" if only because of his soaring ambition and flamboyant style, attributes that on occasion have made him a figure of fun on Fleet Street and perhaps obscured his very considerable ability, not to mention the strength and coherence of his views. He is a tall, pencilslim, aquiline figure with a huge pile of blond hair that tumbles regularly over his forehead and has fetched him such labels as "Tarzan" and "Hair apparent." (The hair has quite recently appeared to have been cut shorter.)

Most Tories consider Heseltine their best and most effective platform speaker. As defense secretary, he would assault a potential Labor government's stewardship of the armed services in derisive language such as: "Over the top, lads -- just wait for the tea break. ... If you want to turn that thin red line into just some sordid demarcation dispute, then I tell you, let the unions loose in the armed services. ... It is not a joke. Services on strike. Licensed mutiny."

Like many powerfully motivated people, Heseltine's relentless climb toward the top of the tree was undertaken on his own. A loner, he is also a self-confident and strong presence, never as comfortable, it seems, as when he is put in charge of something. He has been called an American-style politician running for an increasingly presidential office. And he's been called a rabble-rouser of the gentry, although his appeal would appear to lie more with the middle than the upper classes.

Over the past year or so, as Mrs. Thatcher became vulnerable, Heseltine's every word and deed seemed so carefully calculated as to give a somewhat counterfeit aspect. Still, he managed somehow to keep faith with the views that have defined his differences with Mrs. T., and a good many Tories now believe that he would be a strong party leader and a first-rate prime minister. In endorsing Heseltine on Thursday evening, after Mrs. Thatcher's resignation, Lord Carrington, who is as sensible and prestigious a figure as the party has, seemed to be saying just that.

Heseltine's views on security issues are orthodox, and he supports the current allied position on the Persian Gulf crisis. However, whereas Mrs. Thatcher was out in front of everyone, including President Bush, with regard to the use of force there, whoever succeeds her is likely to adopt a less hawkish public position. Far more revealing will be Britain's approach to a meeting in three weeks of the members of the European Community for the purpose of amending the Treaty of Rome so as to clear the way for a monetary union that would include a central European bank, or Euro-Fed, (by 1994) and further down the road a common currency. It's unlikely that Mrs. Thatcher's successor will allow Britain to stand apart from whatever the other members decide on. Nor would any one of them be expected to share her view of the EC's plans as designed to envelop members in a crypto-socialism and strip them of their bedrock sovereignty. Heseltine and Douglas Hurd, the foreign secretary, have always favored a stronger role for Britain within a cohesive EC; Heseltine, of course, chose to resign on a European issue. Chancellor of the Exchequer John Major, their rival, is by now probably not far from them in his formal European attitude.

Heseltine's opponents have some advantages: Hurd has had broader and deeper ministerial experience than either of the other two. Major is wholly a creature of the Thatcher experience, which could help him. Heseltine points to polls that show him as having the best chance of winning a general election. And since he has opposed Mrs. Thatcher's regressive and widely despised poll tax, he can promise plausibly to fix that. Heseltine can also claim to be the one who accepted all the charges of disloyalty and took all the risks that accompanied the most dramatic event within the Conservative Party since 1940. Moreover, only he among Tory leaders has been able to set forth an independent body of views in recent years. His colleagues within the parliamentary party, when they vote, can be fairly sure that what they see, warts and all, is what they would get from Michael Heseltine.

John Newhouse is a staff writer for The New Yorker.