I don’t know the Senate rules for expelling a member, so bear with me.
Under what justification would they try to expel Moore if he gets elected?
If someone is elected in a free and fair election, there better be a damn good reason for even suggesting not seating or expelling someone.
After all we have gone through with Bill Clinton, there would actually be some move to expel someone over unsubstantiated allegations from decades ago? Allegations which were never ever brought into the legal system???
This is dangerous territory if we go there, in my opinion. Then you can expel anyone for any reason, on any trumped up charge. That is not who we are, if I can paraphrase Obama; that’s not how this country operates, to get rid of a member of Congress for no actual legal reason.
Under what justification would they try to expel Moore if he gets elected?
It takes 2/3rds of the Senate to expel a member, something that hasn't happened since the Civil War. Several have resigned since then rather than face expulsion. Seeing how seemingly every GOP Senator loathes Roy Moore, it would be fairly easy to come up with a 2/3rds vote for expulsion.
The Senate can expel a member for anything or nothing, at any time. Obviously, the reason given will be these current charges of sexual impropriety for actions that may or may not have happened 40 years ago but the real reason is under no circumstances does the GOP want Judge Moore in the Senate. He's a swamp-drainer. They want Luther Strange. He's part of the club, and there may be a path for Strange to return to the Senate if Moore is expelled.