[DoodleDawg]

He'd have to successfully challenge Mississippi's "sore loser" law that prohibit such write-in campaigns.

I believe the law says that having lost in the primary, McDaniel can't be on the ballot as an independent or representative of any party. But does that prevent people from writing in his name? And if enough people did that then could they really prevent him from taking the seat? A colossal long-shot to be sure, but it worked for Murkowski.

[Black Agnes]

The votes aren’t counted for write-ins. Wouldn’t matter how many he got.

[Drew68]

And if enough people did that then could they really prevent him from taking the seat?

That would really get into uncharted territory. For one, there's probably several Chris McDaniels in Mississippi. Should a "Chris McDaniel" win a write-in campaign, would not any one of them be able to step forward and try to claim the Senate seat?