WASHINGTON (CNN) -- Former New York City Mayor Rudy Giuliani filed papers to form a federal exploratory committee this week, the latest step towards a possible bid for the Republican presidential nomination.

"It is a mere formality for all potential candidates looking at a possible run," a senior Giuliani advisor tells CNN. "It is akin to crossing the "T" in exploratory."

Earlier this month, Giuliani formed a presidential exploratory committee with the New York Department of State. The latest filing, with the Federal Election Commission, occurred on November 20. John H. Gross, a partner in the law firm Proskauer Rose, is listed as the committee's treasurer.

By forming an exploratory committee, Giuliani can raise money to pay for travel and polling as he considers a White House run. Arizona Sen. John McCain is the only other Republican to form a presidential exploratory committee. On the Democratic side, Iowa Gov. Tom Vilsack has already filed papers to run for president.