Bracepac contributed to 53 Democratic candidates and 50 Republicans in the 2006 election cycle, federal records show.

Some Republican insiders said the campaign contributions by Giuliani's firm will have no influence on the former New York City mayor's attempts to woo conservative and grassroots voters away from the other leading GOP presidential candidates, Arizona Sen. John McCain and former Massachusetts Gov. Mitt Romney.

"If the donations were in Rudy Giuliani's name, or his wife's name, that would be a problem," said Bill Whalen, a Hoover Institution research fellow and former speechwriter to Republican Gov. Pete Wilson. "But it's the reality of modern-day politics ... and under the larger category of doing business. He's a partner in a law firm that wants to do business on both sides of the street -- so you give to Republicans and Democrats."

Giuliani is among a group of 2008 presidential hopefuls who are in California this week for fundraising and public events including Democrats John Edwards of North Carolina, Sen. Hillary Rodham Clinton of New York, Sen. Barack Obama of Illinois and Republican McCain.

As the already busy presidential campaign gathers speed, the hopeful candidates are certain to face increasing scrutiny on their lives inside and outside of politics including issues such as the political contributions by the former mayor's law firm.

Giuliani already has faced questions about his income from the law firm, as a security consultant and as a public speaker, a field in which he reaped $11.3 million last year, federal records show.

The Houston Chronicle reported this month that Giuliani has been paid at least $1.2 million by Bracewell & Giuliani. Texas Lawyer reported that he also received $690,000 in partners' profits last year.

Scott Segal, a partner in Bracewell & Giuliani, said Tuesday in response to questions that the firm's "approach to government relations is bipartisan and bicameral."

Indeed, the firm's political donations are controlled entirely by its political committee. Insiders point out that Giuliani is not a member of that committee and makes no decisions related to its political contributions.

Maria Comella, a spokeswoman for Giuliani's campaign, said in an e-mail Tuesday that "the PAC is not representative of the mayor's beliefs," adding that "people donate to Mayor Giuliani based on their belief in his candidacy, not the other way around."

Bracewell & Giuliani has also been a high-profile lobbying firm, receiving nearly $6 million in lobbying fees last year with a client list that included the National Petrochemical and Refiners Association - which fought regulations to reduce greenhouse gases - and the Electric Reliability Coordinating Council, an industry group formed in part to fight pollution controls for coal-fired plants.

Giuliani's chief policy adviser, Bill Simon - a former Republican candidate for California governor - said he expects Giuliani will be subject to examination by the public in the campaign and believes voters will fairly judge the former mayor's experience and long record of public service.

"I think any presidential contest is going to involve a lot of scrutiny, and the mayor has been a very, very successful individual on a number of different activities," Simon said. Opponents and the media "will look hard at the mayor's record and occasionally distort it."