In his campaign, Obama says he wants to crack down on overseas tax havens and stop allowing hedge funds to pay a 15 percent capital gains rate on most income, rather than the 35 percent income tax rate..

Obama's billionaire finance chair, Penny Pritzker' family fortune:

"I call it taking a bowl of spaghetti and untangling it," Thomas says. "We don't know of anyone who's undertaken something with the complexity of this."

The breakup is well under way. Trott's Goldman Sachs Capital Partners, the private equity arm of Goldman Sachs, plus an investment firm affiliated with Wal-Mart Stores Inc. Chairman Rob Walton, has spent $1.1 billion for a minority stake in Global Hyatt. In total, Hyatt may be worth $11 billion, says Ted Mandingo, owner of an Elmhurst, Illinois-based hotel consulting firm.

Selling Assets

The Pritzkers sold chewing tobacco maker Conwood Co. to Reynolds American Inc. for $3.5 billion in 2006. That year, they tried and failed to shed Triton Container International Ltd., a shipping container company, for as much as $2.5 billion. And Penny says they've sold a significant portion of a $5 billion real estate portfolio that she developed.

The Pritzkers own 80 percent of a partnership that holds a 15.6 percent stake in Royal Caribbean Cruises Ltd. The family portion was worth $719 million on Aug. 19. The Pritzkers list eight casinos on company Web sites. The casino licenses alone are worth $500 million each, says John Kindt, a University of Illinois business professor.

Next year, the family will open a Grand Hyatt hotel and casino with 2,973 rooms just north of the Bellagio hotel in Las Vegas.

In six years, by the time Buffett buys the other 40 percent of Marmon, he'll have spent $10 billion-$11 billion to acquire that company, Trott says.

Buffett says he was so confident in the financial analysis that the Pritzkers developed for Marmon that he decided during a flight from San Francisco to Omaha to buy it.

"It came with a price attached,'' Buffett says. "In the end, we could meet it."

All told, the Pritzker empire is worth as much as $40 billion, a person familiar with the situation estimates.

The family's offshore accounts prevent anyone from getting a complete picture of their wealth. In 1986, when Abram Pritzker died, his heirs claimed an estate worth $25,000. The Internal Revenue Service sued to collect $53 million in back taxes. The two sides settled in 1994 for $9.5 million, according to U.S. Tax Court records.