Based solely on 8-year old rumors and gossip the paper that endorsed him now throws slime on his reputation. Of course McCain denies the New York Times-published allegations vehemently. See video of McCain's denial here.
There are actually no direct allegations of any sexual scandal here, and mostly attacks his ethics on dealing with lobyists. The allegations are paper thin, and should be easy enough to brush off. Its curious to me though, why the NY Times ignored the allegations against John Edwards. The allegations have no meat, but they decided it would be fit to be front page above the fold. Anonymous sources delivering nothing of substance is just irresponsible.
Will this hurt McCain? Not at all. First, this is even older than the smear job the Times did on Rudy Giuliani last year. Second, they don't have a single named source for this story. Third, the Times left out numerous examples where McCain acted against the interests of Iseman and her clients. The effect is likely going to produce more support for McCain among the GOP base, especially given the egregious and salacious nature of the controversy.
Looks like the story is fizziling out with liberals and conservatives alike.