Bad in so many ways.

Former Mayor Rudy Giuliani is expected to announce Tuesday he is not running for U.S. Senate or anything else in 2010, effectively ending his storied – and often stormy – electoral career, The Daily News has learned…

Ironically, however, Giuliani’s decision not to run will almost certainly benefit the Democratic Gillibrand more than anyone.

The former mayor’s step back all but assures that the freshman Gillibrand, appointed earlier this year by Gov. Paterson to fill Secretary of State Clinton’s old seat, will not face any big-name GOPers.

“Her path is now cleared,” enthused one Democratic operative…

Had Giuliani run for Senate, all his scandalous baggage – which includes his former top cop, Bernard Kerik, who last month pleaded guilty to accepting home renovations from a mobbed up contractor – would have been unpacked again.

Yes, all his scandalous baggage — which has been public knowledge for years and years and yet he still led Gillibrand by double digits in three separate polls over the past month. You’re never going to get an environment better suited for a GOP pick-up in New York than next year: Gillibrand’s largely unknown, the national mood is anti-Democratic, and there’s a challenger available with national name recognition who’s largely in line with New Yorkers on social issues. A Rudy win would have given the party a foothold again in the northeast and a voice with a Senate megaphone to challenge Obama on detainee issues, for starters. And of course it would have undercut the media stereotype that the GOP is a small tent that’s dominated now by tea partiers and the like. All that, up in smoke.