Rudy Giuliani’s precipitous fall in recent weeks, from Republican frontrunner to a humiliating withdrawal, was the result of poor advice, an ever-shifting strategy and a candidate who never really got into the fight.

Mr Giuliani, who finished a distant third in Florida — a state he had banked all on to keep his candidacy alive — now looks back on a campaign in which he went through more than $50 million (£25 million) to end sixth in Iowa, fourth in New Hampshire, sixth in South Carolina, sixth in Michigan — and with a net result of one delegate.

On a flight to California, the former Mayor of New York used his remaining political capital to endorse his rival John McCain. “I had to make this decision who I thought the other best candidate was. I think I made it clear in a debate that, had I not been running, I’d be supporting John McCain,” he said, adding: “He is an American hero, and America could use heroes in the White House.”

Mr Giuliani’s demise was in many respects not the result of his three marriages and his pro-abortion, anti-gun, pro-gay-rights stances — the things that many believed would sink him in a primary race where conservatives hold significant sway. At the end of September, on top of the national polls and with nearly $17 million in his coffers — more than any of his opponents — he still had a good chance of capturing the nomination. He had gone a long way to inoculating himself from charges that he was socially liberal with his ultra-hawkish stance on terrorism, and with a campaign founded on his impressive performance in New York after the September 11, 2001, attacks.

The politically secular and taxhating terrain of New Hampshire seemed custom-made for Mr Giuliani’s socially moderate and fiscally conservative persona, especially as Mr McCain was still hurting in the autumn from his campaign’s latesummer collapse. But he was surrounded by a close circle of New York aides who had never run a national campaign — and in September and October they made some fateful decisions.

The disastrous course he was to follow unfolded after a meeting of his top aides in a Times Square hotel in September, including Mike DuHaime, his campaign manager, and his senior adviser, Tony Carbonetti. Realising that he had no hope of taking Iowa because of its heavily conservative Republican electorate, they cast around for a state he could win. They decided that he should concentrate on New Hampshire and Florida.

Mr Giuliani never focused properly on the former because his advisers could not decide if he was running a broad-brush, national campaign or an early-state, momentum-building enterprise. He spent millions in the Granite State on direct mailshots and television advertising, but campaigned there only sporadically. While Mr McCain and Mitt Romney stumped tirelessly before audiences of carefully picked, undecided voters, Mr Giuliani would breeze in for quick, unfocused encounters with untargeted voters, before flying out to fundraising events.

In late December, when it was clear that he was going to lose in New Hampshire, he made the most fateful decision of all: to bank all on Florida. Mr Giuliani quickly became irrelevant to the race while his rivals slogged it out in Iowa, New Hampshire, South Carolina and Michigan. No candidate had ever won the nomination after failing to win a single early state.

Meanwhile, the only press coverage he received was terrible. His close friend and former New York police chief, Bernie Kerik, was indicted on corruption charges. It also emerged that when he was New York Mayor, taxpayers had funded secret trips that Mr Giuliani made to see his mistress, Judith Nathan — now his third wife.

By the time his rivals descended on Florida, he was in freefall. His tough-on-terrorism stance was trumped by the national security credentials of Mr McCain, while Mr Romney’s economic message was more persuasive.

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