Citing financial problems, William J. Bennett announced yesterday that he has changed his mind about becoming chairman of the Republican National Committee and a chagrined White House immediately began a search for a replacement.

Bennett said accepting the post would prevent him from supplementing his salary by giving speeches. In addition, he said he would have to return a six-figure book advance because he could not write the book while serving as chairman and the publisher, Simon and Schuster, would not give him another deadline extension.

Bennett met with President Bush on Wednesday to inform him of his decision. Bennett insisted yesterday that ideological differences with the president or with White House Chief of Staff John H. Sununu played no role in his decision, as some party officials suggested. He declined the job, he said, because legal advice from the administration on outside earnings had changed since he was first approached in November.

"Two weeks ago I got a green light, two days ago I got a yellow-to-red," Bennett said. "I didn't take a vow of poverty."

Large incomes from speaking fees for figures as outspoken and controversial as Bennett are not unusual. In the four months between his post as education secretary in the Reagan administration and director of national drug policy in the Bush administration, he had made $240,000 in speaking fees, according to his financial disclosure statement. Sources said Bennett had been told he could make more than $1 million a year in speech fees to supplement his $125,000 a year as head of the party.

Administration and party figures said Sununu and his top political aide, Edward Rogers, who selected Bennett and persuaded him to take the post, had begun a fast search for a replacement.

Among those mentioned as possible successors are former Republican officeholders and Cabinet members, such as former representative Thomas Loeffler (Tex.), Transportation Secretary Samuel K. Skinner and defeated Sen. Rudy Boschwitz (Minn.), as well as senior political operatives such as Richard Bond, a former deputy chairman of the RNC and longtime Bush political aide who was being heavily promoted by party and some White House officials.

Bennett's decision set off a round of fingerpointing among Republican officials inside and outside the administration who questioned why the financial issue was not addressed before Bush formally announced Nov. 30 that Bennett was his choice to replace Lee Atwater, who is ill with a brain tumor.

"It's Keystone Kops time at the White House," said one official. "The president looks like a fool, thank you very much Bennett, Sununu and Rogers."

Democrats reacted gleefully to the disarray, issuing a mock "Help Wanted" advertisement for the GOP post that listed a "Career Opportunity" for a "conservative with independent wealth or trust fund" and noted the candidate need not have political experience. "I look forward to debating the nation's future with whomever the president now chooses to manage the chaos in his own camp," said Democratic National Chairman Ronald H. Brown.

A former Democrat who is said to harbor presidential ambitions of his own, Bennett was not a favorite of all factions of the party or with some Bush partisans. Sen. Robert J. Dole (R-Kan.) reflected that when he said yesterday, "I thought Bennett was a mistake in the first place. He'd only been a Republican for about four years, never run for office and to me it's got to be somebody who understands and likes politics."

Some Bush loyalists feared Bennett would set up what one called a "neoconservative base camp" at the RNC from which to argue policy with the White House and burnish his presidential ambitions. "Party chairmen should implement the president's policies, not try to make policy," said one party regular outside Washington who was relieved at Bennett's departure. "And it would be nice if the president's chairman had supported his presidential bid to start out with."

Bennett said in an interview that he had been initially reluctant to take the post. "My first answer {to Sununu} was no, then yes. I'd had two books and other things waiting and the advice I got from the White House counsel was you could do all those things. Then the advice changed."

He said Simon and Schuster not only refused to grant him another extension but asked him to return his advance -- listed as $187,000 on Bennett's financial disclosure form -- with interest. In the two years since he got the advance, Bennett had spent the money, officials said, so he would have had to earn or borrow it to return it to the publisher.

"To make the money back," Bennett said, would have involved him in activities that could be viewed as a conflict of interest.

White House Counsel C. Boyden Gray said yesterday it was "not a legal issue" but one of appearances of propriety and that his advice changed as Bennett's description of his plans changed.

"My advice was he shouldn't speak to certain groups" for money, Gray said, and cited Fortune 500 companies and their lobbying arms and groups with clear interest in legislation. "This is not a fine, bright line," said Gray. He said Bennett had extensive discussions about the job with his older brother, Robert, who is special counsel to the Senate ethics committee in its current probe of five senators' ties to savings and loan executive Charles H. Keating Jr.

Gray said Bennett feared "doing that which his brother was arguing was wrong on the legislative side." For his part, Robert Bennett said during a break in the Keating hearings yesterday that he had warned that serving as RNC chairman, advising the White House on policy and earning hefty speaking fees at the same time "was a very combustible mixture."

Robert Bennett said his brother was afraid his actions would create an appearance of conflict of interest even if none existed. During the hearings, Robert Bennett has asserted that senators can be faulted for an appearance of conflict as well as an actual violation of laws or rules.

Some publishing sources were dubious that Simon and Schuster would ask for its advance back since many authors are routinely allowed extensions. Robert Asahina, a vice president of Simon and Schuster and Bennett's editor, declined to discuss the situation yesterday but said he agreed with Bennett's description in a letter he sent to Bush. Staff writers David S. Broder, Helen Dewar, E.J. Dionne and Michael Isikoff contributed to this report.