WASHINGTON — Mayor Giuliani’s top policy adviser, William Simon Jr., does not bring much electoral success to his presidential campaign — he failed in his bid to be California’s governor, twice.

But that is probably not why Mr. Giuliani hired his longtime friend. What Mr. Simon, a wealthy businessman, does bring to the mayor’s campaign, current and former aides say, are deep Republican ties in the nation’s largest state and strong credentials among conservatives.

Mr. Simon has served as one of Mr. Giuliani’s top public backers, introducing him at major speeches and standing beside him at key endorsements. His primary work, however, has been behind the scenes, where he is leading what has been called “Simon University” — a crash course in policy briefings led by top scholars to bring Mr. Giuliani up to speed on major foreign and domestic issues.

The briefings, which occur several times a week and last between one and three hours, mirror the approach Mr. Giuliani took before his successful bid for New York City mayor in 1993, when he developed a broad understanding of city governance along with many of the policies he implemented once in office.

The idea, Mr. Simon and other advisers say, is to give Mr. Giuliani a strong foundation of knowledge on key issues, ranging from tax policy and entitlement reform to Iraq, so he can form specific positions and proposals that will be articulated as the campaign goes on.

“They’re pretty open-ended sessions, in terms of the give and the take,” Mr. Simon said of the sessions. “They’ve been actually pretty interesting.”

As the campaign’s director of policy, Mr. Simon participates in nearly every meeting, but he does not lead the discussions; rather, he has recruited scholars from top conservative think tanks such as Stanford University’s Hoover Institution, the Manhattan Institute, and the American Enterprise Institute.

The son of a former treasury secretary to President Nixon, Mr. Simon, 55, was the Republican nominee for governor in California in 2002 after defeating the mayor of Los Angeles, Richard Riordan, in a primary. He lost to the Democratic incumbent, Gray Davis, but he ran again the next year in the historic — and chaotic — recall election. Mr. Simon dropped out of the race more than a month before the election, however; at the time, he cited a crowded Republican field, which included the eventual winner, Arnold Schwarzenegger.

Among followers of Mr. Giuliani’s career, Mr. Simon is perhaps best known as a bit player in the day that has come to define the former mayor in the eyes of many Americans: September 11, 2001. The two men were having breakfast at a hotel in Midtown Manhattan, discussing Mr. Simon’s gubernatorial ambitions, when the first plane hit the World Trade Center. After being told of the incident by an aide, Mr. Giuliani excused himself and rushed downtown.

The two men’s friendship dates back to the 1980s, when Mr. Simon worked as a federal prosecutor under Mr. Giuliani, who was U.S. attorney for the Southern District of New York.

In a recent telephone interview, Mr. Simon said he has not detected much of a change in his former and now current boss in the last 20 years. “He’s very energetic,” he said of Mr. Giuliani. “He wears out people far younger than him. He’s a very stimulating and provocative person to be around.”

He said he has come away impressed with Mr. Giuliani’s demeanor during the policy briefings.

“Sometimes I shrug my shoulders when people call it Simon University because it implies that Rudy is starting off at square one, which is not the case,” Mr. Simon said.

Aides describe Mr. Giuliani as very engaged during the briefings.

“It’s the mayor asking questions: ‘What about this? How does that work? What’s your opinion of what ought to be done? Why this rather than that?'” the campaign’s chief economic adviser, Michael Boskin, said.

The Manhattan Institute scholar who organized policy briefings for Mr. Giuliani before his run for mayor, Fred Siegel, said Mr. Giuliani would want to make use of the experts without relying on them. “What he’s looking for is to develop a capacity for judgment” on a particular issue, he said.

Mr. Siegel, who later wrote a book about Mr. Giuliani’s mayoralty, “The Prince of the City,” is not advising him in his presidential campaign. He said Mr. Giuliani was also quick to recognize when someone was trying to advocate rather than inform. “He was not someone you could put one past,” he said.

While Mr. Giuliani has yet to issue any specific or detailed policy proposals, discussions that began during the policy briefings Mr. Simon is organizing have begun to seep into the candidate’s public statements.

During a session with military experts on the Bush administration’s “clear, hold, and build” strategy for securing Baghdad, Mr. Giuliani drew comparisons to crime-fighting techniques that he and top police officials implemented when he became mayor of New York. He has since used the comparison in describing his position supporting President Bush’s decision to send 21,500 additional troops to Iraq.

Beyond Mr. Simon’s policy work, aides say the adviser’s business connections and ties to the Catholic Church will be an asset to Mr. Giuliani in California, a state with a new early primary that will be key to his hopes for the nomination, especially if he does not win in Iowa and South Carolina, which are considered more conservative.

Mr. Simon also is more conservative than Mr. Giuliani on social issues, and the former mayor is trying to ease the concerns of voters on the right who may be wary of his more liberal views on abortion, gun control, and gay rights. “He brings credentials — conservative credentials, business credentials, and Catholic credentials,” Mr. Simon’s former communications director, K.B. Forbes, said.

Mr. Simon, who lives in California but is often with Mr. Giuliani in New York or on the road, splits his time between the campaign and work on his business and nonprofit interests. Whether he would follow Mr. Giuliani to Washington to serve in his administration is another question — and the answer, not surprisingly, is a long way off. “I haven’t thought about it,” Mr. Simon said with a laugh.