BBC News, New York
Rudy Giuliani is in the race for the 2008 White House, although the always unconventional former mayor of New York has yet to make a formal declaration.
Could Mr Giuliani and Mrs Clinton be battling it out for the presidency?
However reluctant he is to stand on a podium downtown or stage a webcast, the hard figures have made a Giuliani run inevitable for some months now.
In a national poll published last Wednesday he was 16 points ahead of his nearest rival for the Republican nomination, Arizona senator John McCain.
For somebody who has never held political office in Washington or run his home state, his national profile is extraordinary.
And now New Yorkers are looking forward to the tantalising prospect of - in effect - hosting the next presidential election.
If Mr Giuliani secures his party nomination and Democratic front runner Hillary Clinton secures hers, it will be a re-run of the much-anticipated New York senate race of 2000 which never materialised.
Mr Giuliani withdrew and Mrs Clinton romped to victory.
Although the primary battle is unlikely to be resolved until next summer, Manhattan politicos are already talking about a political "subway series" - the term used to describe a run-off between the city's rival baseball giants.
Wednesday's national poll showed Mr Giuliani with a two-point edge over Mrs Clinton, but a different poll published that day - surveying New Yorkers only - showed Mrs Clinton ahead of her old rival by 10 points, 50-40.
'Man of the hour'
On 10 September 2001, Mr Giuliani's political career seemed to be in terminal decline.
The 9/11 disaster made a national hero out of Rudy Giuliani
His second, fractious mayoral term was drawing to a close.
His second marriage was already over and still dragging acrimoniously through the divorce courts and he was recovering from prostate cancer.
Then 9/11 changed everything and he emerged, caked in the dust of the World Trade Center, as America's mayor.
More than five years on, re-building at Ground Zero is still in its infancy, but last autumn the first official visitors' centre opened it doors.
One of its founders is Lee Ielpi, the fire department veteran whose own firefighter son died in the wreckage of the towers.
He has come to know Mr Giuliani well and believes that he is now destined to lead the country.
"9/11 brought out the real strength in Giuliani," he said.
"It made people realise that [Mr Giuliani], besides being a commanding-type leader, also had passion and will.
"He'll run this country the same way that he ran this city - being the commander that we want."
'A terrible mayor'
Among the visitors to Ground Zero now, are large numbers of travellers from all over the world, together with many from other states around the US.
Influenced perhaps a little by the scene in front of them, most Republican voters interviewed said Giuliani was their first choice for the nomination.
But talk to a random selection of mainly Democrat-supporting New Yorkers walking briskly along the pavements of downtown and it's a very different story.
"I think it makes us New Yorkers look stupid that we would follow so blindly along this arrogant politician," said one jewellery designer in her 20s.
"He was a terrible mayor," said another expensively-dressed woman in a hurry.
Despite his reputation as the aggressive crime fighter and moralising killjoy of New York's nightlife, many of his social policies do not sit well with the electorates of rural America.
He is still pro-choice on abortion, but in recent interviews he has begun to move distinctly rightwards in an effort to convince the Republican base of his true conservative instincts.
'Tetchy' media relationship
Wayne Barrett has been covering Mr Giuliani for more than 25 years as a senior editor on New York's venerable news weekly, Village Voice.
Wayne Barrett says a Giuliani presidency would be disastrous
As a high profile government prosecutor, he admired Mr Giuliani but the politician's idealism of old quickly gave way to vainglorious cynicism once he landed in City Hall, Mr Barrett believes.
Following on from an investigative biography, Mr Barrett recently co-authored a book which acidly warns America what a Giuliani administration might do to the country.
The title pulls no punches. Grand Illusion - The Untold Story of Rudy Giuliani and 9/11.
"No-one's ever run for president on the strength of their performance on a single day, but Rudy seems to think he can do that. While he did hit all the right notes that day - he also made some terrible mistakes," said Mr Barrett.
Mr Giuliani admits to some mistakes, but Mr Barrett - along with several union leaders - believes that many of the firefighters need not have died on 9/11 if the mayor had taken the terror threat seriously in advance and placed his joint command centre somewhere other than the World Trade Center.
Mr Giuliani had a famously tetchy relationship with the New York media, and there is a reflexive scepticism here towards politicians and power which is rarely found elsewhere in the US.
But Mr Barrett is convinced that a Giuliani presidency would be disastrous and says the evidence is there for all to see and read, starting with his behaviour since becoming the hero of 9/11 in the place of a missing President Bush.
"The iconic image that emerged not only created Giuliani Partners - a multi-million dollar consulting business that's by and large based on his 9/11 reputation - but it's propelled him to become a serious candidate for president," said Mr Barrett.
It is certain that once this already energised campaign season gets fully off the ground, neither Mr Giuliani or Mrs Clinton will be shown any mercy when it comes to airing the voluminous laundry of the past.
New Yorkers - savouring their home advantage - can hardly wait.