It's funny that I can't be sure what you mean by "unlikely to cost him the election". That can be taken two ways. Either nobody minds him taking foreign money, or he's already doomed and thus nothing can cost him the election.
I meant to imply a third option: that folks wouldn’t trust the story anyway, at least not enough for it to influence their vote. This isn’t like, say, the Clinton email issue, which was being pushed heavily even by the NYT. This would’ve just been another right wing “scoop” that didn’t do much until it got censored.
Nobody who isn’t too far gone on the Trump Train thinks the bribery story is anything but horse shit. That’s what “unlikely to cost him the election” means.