Sen. Barack Obama's wealth more than doubled during his presidential campaign — and shot up 10-fold since he entered the U.S. Senate three years ago, his financial disclosure filed yesterday shows.

Obama is the least wealthy of the remaining presidential candidates. But with advances and royalties from two best-sellers, Obama's assets were worth between $2.02 million and $7.35 million at the end of 2007, his public financial disclosure report filed with the Federal Election Commission shows.

For the same period in 2006, Obama's holdings were worth $455,000 to $1.125 million. When he entered the U.S. Senate in 2005, he reported assets worth between $200,000 and $400,000.

Obama's wealth does not match that of Democratic rival Sen. Hillary Rodham Clinton, who has loaned her campaign $11.4 million and who along with President Clinton have earned more than $100 million since he left office at the start of the decade.

Nor does Obama match Sen. John McCain, the presumptive Republican nominee. McCain's wife, Cindy, inherited her father's Anheuser-Busch distributorship in the Phoenix area. Although the McCains' holdings are separate, the family wealth is thought to be between $28 million and $100 million.

Obama's money has come largely from sales of his books, "Dreams From My Father" and "Audacity of Hope." He's also writing a children's book. All three of the candidates have had best-sellers.

Obama's money is mostly invested in conservative treasury notes and bond funds, one of which was worth $1 million to $5 million, according to the forms, which require disclosure of a range of values.

His mutual funds include so-called socially responsible funds, screened to meet certain "criteria." Those funds have major stock holdings in banking and technology companies.

Obama released his latest tax return last month showing he and his wife, Michelle Obama, earned $4.2 million in 2007, driven primarily by book sales. His income had been less than $1 million in 2006.

Jack Pitney, a political scientist at Claremont McKenna College, said that while there are no conflict questions related to Obama's writings, his wealth could present him with a political problem "because of the issue of elitism," a charge he has sought to fend off during the primary."