The New York Senate race always promised to be one of the great American landmark political events of the year. No-one in the city or the state is neutral about the two candidates pitted against each other in this gladiatorial contest: Mayor Rudolph Giuiliani, the combative figure credited with cleaning up the city or turning it into a fascist state; and Hillary Rodham Clinton, feminist idol and victim or scheming harpie, depending on your view point.
But Mr Giuliani's shocking report yesterday that he had been diagnosed with prostate cancer throws it wide open, at a time when there were already questions about whether he was the best man to fight the First Lady. It is by no means certain that he will not run - he does not seem to have decided himself. But if he stands down, it will have huge consequences for the election.
Mr Giuliani is a polarising figure, credited by his supporters with cleaning up the city, cracking down on crime first as a District Attorney and then as Mayor since 1993. He has a brusque and rude manner, confronting his enemies directly. But his tough 'zero-tolerance' policies have also earned him plenty of adversaries. The shooting of several unarmed black men have sparked allegations of racism and police abuses.
He does not shoot from the hip; he steadies the weapon and fires until the magazine is empty. After immigration agents seized the Cuban boy Elian Gonzalez last week, the Mayor said the government had "trampled the wishes of his mother this morning with guns and with storm troopers, bringing a sharp retort from Mrs Clinton.
"I think that the mayor's inflammatory and divisive rhetoric is part of a pattern that he has engaged in for quite some time," she said.
His personal life is opaque. Mr Giuliani's wife, with whom he is no longer close, is an actress, Donna Hanover. She announced last week that she will join the cast of the play 'The Vagina Monologues', a controversial play by Eve Ensler, a friend of Mrs Clinton.
Some in the party had already suspected that he might not run. Rick Lazio, a Republican Congressman who had campaigned for the party's nomination, is the obvious choice to step into the Mayor's shoes, and he has publicly said he was ready to run before the Mayor's illness was disclosed.
"If I can make a fair case to Republicans in New York to get the nomination I will be back in this race," he said earlier this month.
Mr Giuliani had lost some support after the police shootings and other incidents which dented his image in the state, and Mr Lazio had suggested that the party should dump Mr Giuliani.
"I think that's up to the Republican leaders," said Mr Lazio.
"They're going to have to look at the slipping poll numbers for the mayor."
New York State governor George Pataki had originaly supported Mr Lazio's candidacy, and there was little love lost between governor and mayor in the intensely personal world of New York politics.
Mrs Clinton has shored up her position in the state after a weak early performance, and she moved this week to discount reports that she only wants the Senate seat as a platform for a run at the White House herself.
"I am going to serve my six-year term as senator. I owe it to the people of New York," she told a town meeting on Wednesday.
The Mayor has a slight lead over Mrs Clinton of about 45 per cent to 44 per cent, according to the most recent poll, but that is statistically insignificant.
Any less well known Republican would face a hard task, both in winning electoral support and in garnering the massive funds needed to beat the First Lady. It might mean a much less interesting race; but it could leave the way clear for the President's wife to gain public office, prolonging the Clinton political dynasty for another six years and more.