It won’t be cheap, so the initial assumption is he must think there is something there, as the votes needed to make up the difference are fairly substantial. Either that, or he’s excessively wealthy, or has excess campaign dollars still lying about, and just wants to find out. But the option is supposedly there for him, if he can afford it.
It would be nice if he just did what most of these guys do and transfer his left over cash to the national GOP, but I guess that ain’t gonna happen.