Treasury Secretary Larry Summers may have concluded by now that some guys do have all the luck. His fabled predecessor Robert Rubin seems to have left the cupboard bare.

The state of Summers's karma matters. He arguably has one of the four or five most important jobs in the world--along with guys named Clinton, Greenspan and Yeltsin. If the financial gods frown at Larry Summers at some point, they frown at nearly all of us. And they are curling a lip his way right now.

A stock market that soared to irrationally exuberant new heights under Rubin has yo-yoed downward under Summers. The strong dollar that helped wring inflation out of the U.S. economy has weakened erratically against the Japanese yen, tearing a hole in international monetary cooperation. And Summers was forced to defend himself in Congress last week against charges that he contributed to the ineffectiveness of U.S. aid to Russia.

This sea of troubles arrives as Summers plays symbolic host this week to the annual gathering here of the world's most important central bankers, finance ministers, private banking executives and the other assorted money men who have some connection to the International Monetary Fund and the World Bank.

Rubin managed these meetings with his customary aplomb, elegantly turning aside European schemes to weaken U.S. domination of the IMF and, to calm the panicky types, repeating that the world's economic fundamentals were solid.

Even in the conservative business attire of his professional tribe of investment bankers and bond salesmen, Rubin always seemed to be wearing winners' racing silks. When Mexico blew up, Russia imploded or Brazil teetered, Rubin's hard-won credibility was important in buying time and confidence to show that things would soon improve.

Rubin stood out in a White House and Cabinet that has--along with a number of impressive and dedicated public servants--its own fair share of egomaniacs, windbags and truth-twisters.

If Rubin told you something that he later discovered was wrong, he would personally take the trouble to correct it in a telephone call. He declined advice to change one of the fundamental rules of accounting for Social Security because he was worried about leaving the impression of "changing the goalposts," a tactic this president and many of his followers have elevated to an art form.

Summers was able in his first months on the job to draw on the capital of having been Rubin's deputy. When I asked him shortly after his swearing-in if it would make any difference to the world that an academic without the business experience of a Rubin was now in charge, Summers reasonably pointed out that he had closely collaborated with Rubin on all major policies and would bring continuity.

But the personal differences between the two men argued that things would not stay exactly the same, and they have not.

Summers's manner is hot where Rubin's was cool. Summers's strength lies in provoking rather than in reassuring. He has ascended to the highest ridge line of power more through what he has recently learned (much of it from Rubin) than through what he naturally is.

Rated as one of the nation's most intellectually brilliant economists while he was at Harvard, Summers for years had the reputation of being politically tone deaf.

While at the World Bank, he penned a memorandum in 1991 that cited the economic logic of shifting industries that produce "health-impairing pollution" to developing countries desperate for jobs and revenue. In his first years at Treasury, he was famous for aggressively hectoring politicians, journalists and Japanese bureaucrats who did not see things as clearly as he did. If I got a call from Summers, I could be sure it was not because he thought he had gotten something wrong.

But as Rubin's departure came closer, Summers worked mightily and successfully to restrain both temper and ego, to build bridges rather than nuke them and to project a more statesmanlike vision and personality than your average Clinton wonk. He was easily confirmed by the Senate.

This may have been nothing more than the sanding down of rough edges. But Summers labors to occupy positions and attitudes that came naturally to Rubin, who communicated his ease with himself and his ideas to his global audience. The world's money men will this week be closely eyeing Summers' baptism of fire with the yen, Russian misadventures and Wall Street's stumbles. Suddenly, Larry Summers is on his own.