Rudy Giuliani formally dropped his presidential bid and endorsed John McCain Wednesday, setting up the Arizona senator with valuable support and big press heading into Super Tuesday, Feb. 5.

Giuliani pledged to campaign with McCain wherever he is needed, and touted his former rival as an "American hero" and "the most qualified candidate to be the next commander in chief of the United States."

Giuliani spoke at the Ronald Reagan Presidential Library in Simi Valley, Calif., where the Republicans had been gathering to debate Wednesday night.

“He came from way behind to go way ahead, and once again displayed his tenacity, his courage, his ability to focus, his ability to get things done," Giuliani said, referring to McCain's surge over the past two months. "I can’t imagine a campaign that better demonstrates who the person to be president of the United States should be."

On his plane en route to The Golden State, the former New York City mayor said that he opted to end his faltering campaign because he did not want to eat into McCain's support on Super Tuesday, when just four remaining candidates will battle for the 1,023 delegates allocated from 21 states voting that day.

"It's disappointing to lose a race for president because you believe you're the best candidate, but I had made it clear before I had to make this decision who I thought the other best candidate was," Giuliani said.

As Giuliani exits, McCain, Mitt Romney, Mike Huckabee and Ron Paul will be scrambling to embody the message espoused by the namesake of Wednesday's debate site.

For McCain, appealing to conservative voters is a must. Though he won the Florida primary Tuesday on the backs of several powerful voting blocs, exit polls showed conservatives trended more toward Romney. McCain has been under steady attack from prominent conservatives like former House Majority Leader Tom DeLay and faces the scourge of conservative radio talk show hosts deriding his record in the Senate.

A new ad set to air Thursday from the group Citizens United attacks McCain's positions on tax cuts, gun control and illegal immigration, calling him "surprisingly liberal."

"It's to educate the American people ... that John McCain is not a conservative, never has been a conservative. He talks the talk but he's never walked the walk," Citizens United President Dave Bossie told FOX News Wednesday.

Wednesday's debate was also the last chance for Romney to try to topple McCain as the presumed front-runner before Super Tuesday, Feb. 5. McCain is riding a wave of momentum from his victories in Florida, South Carolina and New Hampshire, while Romney has pursued a more low-key quest for delegates, winning Michigan, Nevada and Wyoming.

Romney said on FOX News that the choice for voters is either McCain, "or do they want to vote for me -- who does his best to bring together the Republican coalition that Ronald Reagan built?"

Romney has frequently pointed voters to his resume in the private sector, as the economy has emerged as the top issue this election year, trumping the Iraq war and illegal immigration. Meanwhile, McCain has sought to cast Romney as weak on national security, and touts his criticism of the war's conduct before the surge as demonstrative of his ability to be commander in chief.

GOP strategist Terry Holt told FOX News that Giuliani's endorsement is "an easy fit" for McCain.

"The two national security agendas are very similar," he said. "I think most of the voters who were going for Giuliani will probably end up going for McCain ... it reinforces his position as the frontrunner in the race."

McCain's victory in Florida sets up the GOP contest as a presumed two-person race, but Huckabee, who won the Iowa caucuses Jan. 3, is not giving up the fight.

After placing fourth in Florida, Huckabee said he'll be concentrating on southern states Feb. 5.

"Quite frankly we have a scenario in which we could still win the nomination," he said. "We think we're in this thing for the long haul ... I'm still sluggin' away for the gold medal."

On the plane to California Wednesday, Giuliani told reporters there was no quid pro quo involved in his endorsement of McCain.

"I’m not seeking the vice president nomination. It’s way too premature for anybody to be speculating about vice presidential candidates. I’m not seeking a position in government," he said.

As to why he stuck with his failing strategy of waiting out other early voting states to focus on Florida, where he finished third Tuesday, Giuliani said he had no other choice.

"Obviously the strategy didn’t work. So we’re going to go back and try to figure out why. I don’t have the answer for that ... It was the strategy available to us. It was the only realistic strategy available to us given my strengths, my weaknesses, given the amount of money we were able to raise, and given the places we thought we could make a big impact."

Click here to read more about Giuliani explaining his decision to drop out and endorse McCain.

FOX News' Mosheh Oinounou contributed to this report.