Making the most of his front-runner status, former New York Mayor Rudy Giuliani on Monday moved closer to a 2008 campaign for president, adjusting his paperwork to file a "statement of candidacy" with the Federal Election Commission.

Click here to see the statement of candidacy.

As a result, Giuliani remains in the "exploratory" stage, but the removal of words like "testing the waters" from his filings puts him in full swing to win the Republican nomination to be president.

• Watch an exclusive interview with Giuliani on FOX News' Hannity & Colmes tonight at 9 p.m. ET.

Giuliani, who earned the title "America's mayor" for his response to the Sept. 11, 2001, terrorist attacks, now has more legal room to raise and spend money. The decision to go full throttle into the 2008 race comes earlier than he had planned and sends a signal to skeptics that he is serious about a candidacy.

In fact, Giuliani had wanted to hold off making an announcement for candidacy, but with the growing field of Republican candidates diverting attention far and wide, Giuliani was forced to make the most of the public relations move that accompanies an FEC filing.

Click here to visit's You Decide 2008 center.

When Giuliani first filed papers in November to create an exploratory committee, he made sure to note that he was not full swing into the race. The provision that he was "testing the waters" allowed him to move forward without any commitment to seek a top spot on the ticket or the need to identify donors.

The step Monday puts Giuliani on the same level legally as Arizona Sen. John McCain and former Massachusetts Gov. Mitt Romney, both who have filed statements of candidacy and are running near Giuliani at the top of opinion polls on Republican preferences for the nominee.

In the most recent FOX News poll, 34 percent of registered voters surveyed said they would vote for Giuliani in the 2008 GOP primary compared to 22 percent for McCain and 3 percent for Romney. Former House Speaker Newt Gingrich won 15 percent of that vote. With 65 percent, Giuliani also was at the top of the list of candidates who voters said they would be at least somewhat comfortable with as president.

Giuliani's cautious and noncommittal attitude has caused some critics to question whether he would abandon his bid even before formally entering the race. Fighting back in recent weeks, Giuliani has started to sound and act like a strong contender, traveling to the early primary 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 GOP 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.

The shift in campaign organization, however slight, is an indication that Giuliani likes the response he's received as he gauges support while traveling the country.

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, and even coming out ahead in many state polls, he still must contend with the conservative base who are most likely to vote in primaries.

He is at odds with the Republican National Committee platform plank that opposes a right to abortion. While he doesn't support gay marriage per se, he has not come out against it and has supported lesser legal rights, like civil unions, for gay couples.

He has also been divorced twice but most of his dirty laundry is already out after a brief flirtation with a senatorial run in 2000. Giuliani is counting on people remembering his record of leadership both before and after the Sept. 11 attacks, reducing taxes and crime and cleaning up the city.

Giuliani also will forever be memorialized running down to the site of the World Trade Center, where two planes crashed into the main towers, forcing them down. Giuliani appeared on the scene looking authoritative with his police and fire commissioners by his side in the midst of chaos.

He was a former U.S. attorney, leading campaigns against organized crime and corruption. He spent two years as the Justice Department's No. 3 post, overseeing all U.S. attorneys, the Drug Enforcement Agency and the U.S. Marshals Service. The Brooklyn native was first elected New York's mayor in 1993.

FOX News' Carl Cameron and The Associated Press contributed to this report.