EW YORK - One day after the most downcast news conference of his career - where he announced that he and his wife were separating - Mayor Rudolph Giuliani regained his fire yesterday, denying reports that he was dropping out of the Senate race and scolding the press for poking into his private life.
The mayor also denied the charge - publicly leveled Wednesday by his wife, Donna Hanover - that he had an affair a few years ago with his then-communications director, Cristyne Lategano.
Still, Giuliani did not exclude the possibility that he would end his run for the Senate, saying he must still decide what kind of treatment to undergo for his prostate cancer, which was diagnosed two weeks ago, and then determine whether he would have the stamina for a campaign.
''I've made a lot of important decisions,'' the mayor and former federal prosecutor said. ''I've learned you make those decisions when you have to make them. I don't have to make it now.''
Meanwhile, top Republicans - including Governor George Pataki, state Senate Majority Leader Joseph Bruno, and presidential candidate George W. Bush - rallied around the embattled mayor as their only choice to carry the banner in the contest against first lady Hillary Rodham Clinton.
Some Republicans continued to put out feelers about alternative candidates. But unless the mayor drops out, the party leaders have decided not to reveal the slightest split or hesitation.
''They're afraid of Hillary winning, above all else,'' said one person close to top Republicans, ''so they don't want to give her a boost.''
A few other Republicans have expressed an interest in running if the mayor withdraws - Long Island congressmen Rick Lazio and Peter King, and financier Ted Forstmann - but few think they could match the war chest, or the growing popularity, of Clinton.
Polls suggest that Pataki could mount a challenge and possibly even beat Clinton, but the governor flatly said last week that he would not run, even if Giuliani did not.
For the moment, Clinton is in an awkward position. She must carry on as if Giuliani will be her opponent, although her strategy will have to change if he is not. At the same time, she cannot remotely attack Giuliani, partly because of her own marital troubles, partly because it would be unseemly to attack a man with cancer.
''I'm going to, out of respect for him and his family, have nothing to say about it,'' Clinton said on NBC's ''Today Show,'' when asked about the mayor's separation.
President Clinton, in Washington, said of Giuliani's problems: ''Everybody in America ought to be rooting for the human side of this to work out. We should wish him well.''
Even New York's new archbishop, Edward M. Egan, was asked about Giuliani at his maiden press conference. Egan expressed ''the greatest sympathy for this good human being who is struggling through two very serious situations.''
The Senate race these past two weeks has been transformed into a nonstop melodrama about the intimacies of Giuliani's life. On April 26, he announced that he had a treatable form of prostate cancer. Less than a week later, he confirmed reports that he has been seeing Judith Nathan, a 45-year-old registered nurse, for nearly a year. On Wednesday, he nervously announced the separation from his wife. A few hours later, Hanover tearily said, on the steps of Gracie Mansion, that their marriage went sour because of the mayor's relationship with Lategano.
Lategano resigned her post a year ago and then became, at Giuliani's behest, head of the city's tourist bureau, which pays $150,000 a year. She has since married.
Rumors of an affair between the two were widely reported three years ago but were never proven. Giuliani and Lategano both denied the rumors at the time. While Giuliani did not directly contradict his wife's words, he said yesterday, ''I definitively answered all these questions ... way back, and it's the exact same answer today.''
Some politicos were privately worried by Hanover's accusation. It is one thing, they said, for the husband in a bad marriage to have an affair; quite another to have wrecked the marriage with an earlier affair, and then to give that alleged paramour a plum city job.
