WASHINGTON – Former New York City mayor Rudy Giuliani, a moderate Republican best known for his stewardship of the city after the Sept. 11 terrorist attacks, has taken the first step in a 2008 presidential bid.

The former mayor filed papers to create the Rudy Giuliani Presidential Exploratory Committee, Inc., establishing a New York-based panel that would allow him to raise money to explore a White House run and travel the country.

The four-page filing lists the purpose of the non-profit corporation “to conduct federal ‘testing the waters’ activity under the Federal Election Campaign Act for Rudy Giuliani.”

The paperwork, dated last Friday, is signed by Bobby Burchfield, a partner at the DC-based law firm of McDermott, Will & Emery, a firm that handles political work.

Giuliani’s spokeswoman Sunny Mindel declined to comment.

One potential rival for the GOP nomination, Sen. John McCain of Arizona, said Sunday he was taking the initial step of setting up an exploratory committee.

Under federal election law, an exploratory committee allows an individual to travel and gauge the level of support for a candidacy without formally declaring themselves a candidate and adhering to all the federal rules of fundraising. An individual who spends money only to test the waters – but not to campaign for office – does not have to register as a candidate under the election law.

The GOP field is expected to grow with Massachusetts Gov. Mitt Romney, Sen. Bill Frist of Tennessee, Arkansas Gov. Mike Huckabee and New York Gov. George Pataki expected to join the presidential fray.