I'm sure I'll get flamed for this, but all these comparisons to Kobe, Vick, and various other NBA and NFL players really aren't applicable, because, sad and unfair as it might be, they are already half-expected to be thugs or morally questionable. Tiger is coming from the game of golf. From his younger days when it was about him, his dad, and mom, to his growing into a man, to his marriage and becoming a father, he has projected a image of a moral, intelligent, and responsible person, and used that image to become not only the greatest golfer and maybe athlete in the world, but the greatest sports hero's and persona's in our lifetime. If he were known a partying, tail-chasing cad from the start, sure he would still be the best golfer, but he would NOT be the Tiger Woods(TM) we know today. As a matter of fact, and as unfortunately racist as this would be, he would have been perceived as a punk black man crashing the white gentleman's game of golf. Sure he would have won tournaments, but he would never have gathered the kind of respect and endorsement bankability that he has.
Nobody is as big as Tiger, so there are no real comparisons here, but I think Phelps and John Daly are cautionary tales. Someone said that since Phelps' transgression was a "crime", it was more serious than Tiger's serial adultery. C'mon. Most people, including me, would take the moral character of a 19yr old kid casually smoking some dope over a serial adulterer who is hurting his family any day. Yet Kellogg showed him the door. John Daly, who had the potential to have as large a following as Tiger (and almost did), was/is a drunk with a gambling problem, hardly a criminal, and his sponsors dropped him like a bad habit.
In reality though, I doubt this will affect his endorsements too much, at least not short term. He is too big and his sponsors have way too much invested in him right now. In the long term though, if he doesn't repair his image and doesn't regain people's respect for him as a man, his bankability will suffer. He'll never be without sponsors, he's too good, but he won't necessarily demand the kind of money he does now or enjoy the position as his sponsor's "flagship" clients. Worse yet, if Tiger's knees, back, or something else finally goes and he is no longer dominant in the game, then who knows. Without being a beloved persona, a washed up athlete isn't really worth much. The damage control being spun now, including the deals to keep Elin, is as much about his long-term appeal than anything.