Monday, December 10th 2007, 4:00 AM WASHINGTON - Rudy Giuliani, on the hot seat Sunday for the most exhaustive grilling of his presidential campaign, doggedly insisted that death threats against then-girlfriend Judith Nathan prompted the NYPD to launch her taxpayer-funded chauffeur services. "These were all based upon threat assessments made by the New York City Police Department ... of what was necessary to protect her life, my life, other people's lives," Giuliani told NBC's Tim Russert. "Every single thing done here was done based upon the assessment of someone else that this was necessary." His explanation of Nathan's police car service doesn't square with Friday's Daily News exclusive report, citing multiple witnesses and a law enforcement source, that she was being protected by city taxpayers months before the affair was revealed in May 2000. "The threats were after" their romance became known, Giuliani maintained Sunday. The only guest on Russert's "Meet the Press," Giuliani endured a withering examination of his personal character and business dealings. To the glee of fellow presidential contenders, the Republican front-runner spent nearly an hour playing defense, attempting to deflect a flurry of questions about his relationship with indicted pal Bernard Kerik and Kerik's mistress Judith Regan, controversial corporate clients and his own tangled personal life. "The baggage is finally starting to catch up with him," a neutral GOP consultant said. Giuliani said again that he did a poor job of vetting Kerik but denied he allowed personal loyalty to trump his judgment. He said he knew Regan was Kerik's publisher but wasn't aware of their Ground Zero love nest in a pad reserved for recovery workers. He defended the activities of his security and legal businesses as "ethical, lawful, decent work," but said he won't release a list of his clients because he's promised many of them confidentiality. Predictably, Democrats piled on. "Rudy Giuliani's refusal to be honest about his shady past is becoming a chronic habit," Democratic National Committee spokesman Dag Vega jabbed. The usually combative candidate was uncharacteristically subdued throughout the grilling. Somberly dressed in a dark suit, white shirt and red tie, Giuliani employed many of the timeworn techniques of damage control. He turned the tables on his inquisitor - "that's a stretch," he politely complained once - and borrowed from the Watergate scandal's signature "mistakes were made" rationale. Stealing a page from Hillary Clinton's script, he wielded a tactical laugh now and then. He blamed the media for hyping the facts, and invoked the memory of a fellow ex-mayor to explain his poor judgment about Kerik. "As one of my predecessors, Fiorello LaGuardia, used to say, ‘I don't make many mistakes, but when I make them, they're big ones.'" That was a reference to LaGuardia's celebrated 1941 wisecrack: "When I make a mistake, it's a beaut." In a rare interlude from his self-defense chores, Giuliani took issue with GOP rival Mike Huckabee's 1992 remark that homosexuality is an "aberrant" lifestyle. "I don't believe it's sinful," he said. "It's the various acts that people perform that are sinful, not the orientation that they have." The crop of sinners, he added, includes His Honor: "I've had my own sins that I've had to confess and had to deal with and try to overcome, and so I'm very, very empathetic with people, and that we're all imperfect human beings struggling to try to be better."