In a sign that he is serious about running for the White House, the two-term mayor was filing a so-called "statement of candidacy" with the Federal Election Commission. In the process, he was eliminating the phrase "testing the waters" from earlier paperwork establishing his exploratory committee, said an official close to Giuliani's campaign.
The official spoke on the condition of anonymity to avoid pre-empting any disclosure by Giuliani.
Unlike chief Republican rivals Sen. John McCain and former Gov. Mitt Romney, Giuliani has been somewhat ambiguous about whether or not he would ultimately pursue the Republican nomination.
He took the initial step in November of creating a committee to explore a candidacy but added the caveat that he was simply "testing the waters" — a provision that allows truly uncertain candidates to move forward without any commitment to seek a top spot on the ticket or the need to identify donors. At the time, Giuliani also did not file an official statement declaring that he was a presidential candidate.
The steps Monday put Giuliani on the same level, legally, as McCain and Romney, the other two top-tier Republican candidates who have formed regular exploratory committees and filed statements of candidacy.
Giuliani's cautious and noncommittal attitude has caused some critics to publicly question whether he would abandon his bid even before formally entering the race, as he did in 2000 when he was considering a Senate campaign against Democrat Hillary Rodham Clinton.
Fighting back in recent weeks, Giuliani has started to sound and act like a strong contender, traveling to the early primary election states of New Hampshire and South Carolina, and arguing that his vision for the future and performance in the past would make him a formidable Republican nominee.
Still, he has stopped short of committing to a run, insisting that he has to decide whether he can make a "unique contribution" to help strengthen the country — his barometer for whether to run.
"There's a real good chance," Giuliani said Saturday, another coy response to what has been a constant question on the campaign trail.
The shift in campaign organization, however slight, is an indication that Giuliani likes the response he has received as he gauges support while traveling the United States.
Behind the scenes, Giuliani has been busy supplementing his cadre of New York loyalists with Washington-savvy political operatives, establishing a fundraising network, and setting up a campaign headquarters — signs of a campaign moving forward.
Despite being immensely popular in national polls, Giuliani faces hurdles to securing the Republican nomination state by state. His moderate stances on issues such as gun control, abortion and gay rights do not sit well with hard-core social conservatives who are a crucial voting group in the nominating contests, and his two divorces may not either.
Due to his moderate stances, Giuliani's candidacy could test the amount of sway staunch conservatives have in the national party, CBS News correspondent Gloria Borger reports.
And how his positions on those key social issues will be received by primary voters in early states like New Hampshire and Iowa will be closely followed, said CBSNews.com senior political editor Vaughn Ververs. But his near-celebrity status could be a major asset in large states like Florida, California, Illinois and New Jersey – all of which are considering moving up to an earlier date on the primary calendar.
That's a point Giuliani strategist Brent Seaborn makes in a memo posted on the exploratory committee's Web site, pointing to polls which show the former mayor leading the GOP field in those states. "Recent polling continues to suggest Mayor Giuliani is very well positioned within the party – particularly when compared to other potential Republican candidates – to win the nomination," Seaborn writes.
However, many analysts say polls taken this early in the campaign, when voters have little knowledge of all the candidates, are poor predictors of eventual results. "They are measuring celebrity," said Stu Rothenberg, editor of the Rothenberg Political Report. "I just don't believe a whole bunch of people have focused on his record. I don't put a nickel's worth of value in those polls."
Rothenberg said a Giuliani win in the Republican primaries would be a major upset. "The football field is not flat for him," he said. "He's got to run uphill 100 yards."
But conservatives also are not entirely sold on McCain, an Arizona senator, and Romney, a former Massachusetts governor, and that could even the playing field for Giuliani. He hopes primary and caucus voters look past his liabilities and consider his record of leadership in difficult times.
Nicolle Wallace, a former White House communications director and a CBS political consultant, said Giuliani should worry less about specific issues and more about maintaining the positive feelings many Americans feel toward the former mayor.
"His challenge, more than explaining his position on any single issue, will be his ability to run a discliplined, organized, campaign that doesn't result in any erosion of public affection when the campaign gets underway," she said.