As far as sex scandals go, Weiner's misconduct is more tame than outright adultery. Politicians have been caught stepping out on their spouses yet they're not forced from office. Weiner's transgressions, in contrast, don't actually involve adultery, but he probably will not survive this.
He just can't stop himself from emailing pictures of his junk to young women he meets online. He did it before, then resigned from Congress as a result. And he's been doing it again, which seriously jeopardizes his campaign to be New York's next mayor.
It's often a mystery why some politicians can survive sex scandals while others cannot.
Weiner's problem really isn't about sex itself. It's more about addictive behavior. His sexting is habitual and demonstrates poor judgement. I think that's why people aren't very forgiving of him. It seems a given he'll do it again, and people may naturally worry he'd pay more attention to photobombing his crotch shots than running the city.
Sexting is petty and small in a way, so it ends up making Weiner seem foolish and more than a little sleazy. People don't expect an elected official to act like a teenage boy who can't stop posting pictures of his cock online.
We can forgive a lot in public figures, but not everything. I predict this will doom Weiner, not only in this race, but probably in any hoped-for future he might want in politics.